JPH0268489A - Control method for deodorizing device in pre-heating scrap - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for controlling a deodorizing device during scrap preheating.

Arc furnaces are widely used for melting metal materials, but because the metal materials are melted by arc heat, arc furnaces generate high-temperature exhaust gas having a huge amount of sensible heat. The exhaust gas is finally released into the atmosphere after being treated with a dust collector, but if the enormous amount of sensible heat in the exhaust gas is released into the atmosphere without being particularly effectively utilized, it would be a significant waste of thermal energy. It is.

Therefore, the sensible heat of the exhaust gas generated from the arc furnace is used to preheat raw material scrap.
In particular, if the scrap is low-grade scrap such as milling powder or shredder, the exhaust gas after preheating the scrap will contain a large amount of foul-smelling components such as hydrogen sulfide, acetaldehyde, and even styrene caused by the oil and paint of the low-grade scrap. It is included in If such malodorous components are directly supplied to a dust collector, they will not only have an adverse effect on the dust collector, but also cause serious secondary pollution.

For this reason, when preheating scrap, a deodorizing device is generally connected downstream of the scrap preheating mechanism, and the exhaust gas after preheating the scrap is combusted in the deodorizing device while being supplied with fuel to deodorize it. Needless to say, scrap preheating is aimed at making effective use of the sensible heat of the exhaust gas generated from the arc furnace, so it should be done under conditions that save as much energy as possible so as not to go against this perspective. It is required to control the deodorizing equipment.

The present invention relates to a method for controlling a deodorizing device that meets the above requirements.

<Prior Art and its Problems> Conventionally, a deodorizing device for scrap preheating is operated while the amount of fuel supplied to the deodorizing device is always maintained at a constant and maximum level. The malodorous components contained in the exhaust gas after preheating the scrap are greatly affected by the temperature of the exhaust gas from the arc furnace used for preheating the scrap, even if the raw material scrap is of the same grade. The concentration of the above-mentioned malodorous components fluctuates greatly due to fluctuations in the concentration of malodorous components, but in the conventional method of constantly maintaining the amount of fuel supplied to the deodorizing equipment during scrap preheating,
If the amount of fuel supplied is not adjusted to the maximum concentration of malodorous components to the amount necessary for combustion, that is, the maximum amount,
The combustion of the malodorous components becomes insufficient, and eventually the malodorous components -
This is because part of the dust is supplied to the dust collector and then released into the atmosphere.

However, such conventional methods do not have the ability to produce
Since excess fuel is unnecessarily supplied to the deodorizing device, there is a problem in that thermal energy is wasted accordingly.

In reality, considering that scrap preheating is originally intended to effectively utilize the sensible heat of the exhaust gas generated from the arc furnace, it is possible to burn the waste residue after scrap preheating using a deodorizing device while supplying fuel. There is a need for a method for more practically controlling the amount of fuel supplied to the deodorizing device according to the concentration of malodorous components.

<Problems to be Solved by the Invention and Means for Solving the Problems> The present invention provides a method for controlling a deodorizing device that solves the conventional problems such as the problem in preheating a double-blade and meets the needs of the actual situation. It is something.

Therefore, in the present invention, when preheating the scrap using gas from an arc furnace and deodorizing the exhaust gas after preheating the scrap by burning it in a deodorizing device while supplying fuel, the amount of fuel supplied to the deodorizing device is reduced. The present invention relates to a method for controlling a deodorizing device, the gist of which is to control the following in synchronization with the opening/closing signal of the lid of an arc furnace.

An important point in the present invention is that the amount of fuel supplied to the deodorizing device connected downstream of the scrap preheating mechanism is controlled by the opening/closing signal of the lid of the arc furnace, which is the source of the exhaust gas sent to the scrap preheating mechanism. The deodorizing device is controlled in synchronization with the deodorizing device, thereby reducing the overall amount of fuel supplied to the deodorizing device.

Hereinafter, the configuration of the present invention will be explained in more detail based on the drawings.

<Example> FIG. 1 is a system diagram schematically showing one implementation procedure of the present invention.

After the exhaust gas from the arc furnace 11 is post-combusted by self-combustion in the combustion tower 21 and branched off at valves 31 and 32, part or all of it is fed into the scrap preheating mechanism 41. The exhaust gas after preheating the scrap through a predetermined passage is sent to the deodorizing device 151. A fuel supply system 62 with a control valve 61 is piped to the deodorizing device 51, and the opening degree of the control valve 61 is adjusted in synchronization with the opening/closing signal of the furnace cover 12 of the arc furnace 11. A control device 63 with a built-in timer is connected. For example, upon receiving a signal indicating that the furnace lid 12 has changed from open to closed, the control device M63 fully opens the control valve 61, and after 10 to 15 minutes due to the action of a timer, the control device 63 opens the control valve 61 fully.
By opening the control valve 61 to 1/3, the maximum amount or 1/3 of the fuel is supplied to the deodorizing device 51 via the fuel supply system 62 accordingly. The exhaust gas, which has been combusted and deodorized in the deodorizing device 51 under the controlled fuel supply, joins the exhaust gas branched at the valve 31, passes through the cooler 71 and the suction fan 81, and is finally sent to the dust collector. 91 and then released into the atmosphere.

FIG. 2 is a graph illustrating the results of implementing the present invention. In this case, the amount of fuel supplied to the deodorizing device is controlled according to the implementation procedure described above with reference to Figure 1, and in the figure, the vertical axis represents the total hydrocarbon concentration in the exhaust gas (HC1 x 102 ppm).
, the horizontal axis is time (minutes), the broken line indicates the case at the inlet of the deodorizing device, and the solid line indicates the case at the outlet of the deodorizing device.

That is, the furnace lid is opened at time O, closed at time 12, and during this period the initial loading of scrap into the arc furnace is carried out. At the same time, the scrap preheating mechanism is loaded with low grade scrap in advance. However, time 1
Immediately after closing the furnace lid in step 2, the total hydrocarbon concentration in the exhaust gas after preheating the scrap at the inlet of the deodorizing device increases rapidly. This is because relatively low-temperature exhaust gas is sent to the scrap preheating mechanism when the furnace lid is open, and therefore the oil and paint from the low-grade scrap that was in a condensed state just before evaporation is removed when the furnace lid is closed. It is thought that this is because high-temperature exhaust gas is fed into the scrap preheating mechanism and evaporated to -degrees. A similar tendency occurred when the furnace lid was opened at time 30, closed at time 35, and immediately after the furnace lid was closed when additional scrap was loaded into the arc furnace during this period. ing.

In the case of the drawing, the control valve is fully opened by the control device with a built-in timer in response to the signal that the furnace lid is closed for 10 minutes in the time period from 12 to 22 and for 15 minutes in the time period from 35 to 50. During the steady time period, the control valve is controlled to be 1/3 open.

During scrap preheating, when the furnace lid of the arc furnace is opened and then closed, the total hydrocarbon concentration in the exhaust gas after scrap preheating at the inlet of the deodorizing equipment increases rapidly, and this high concentration state gradually increases. We obtained the knowledge that while the total hydrocarbon concentration continues to decrease for a predetermined period of time, during other steady periods the total hydrocarbon concentration remains relatively stable and low. Immediately after the furnace lid changes from opening to closing, for a predetermined period of time, the necessary and sufficient fuel is supplied to the deodorizing equipment to burn all the high-concentration hydrocarbons (malodorous components), that is, the maximum fuel supply is carried out. On the other hand, during other regular periods, the deodorizer is supplied with the necessary and sufficient fuel to burn all the hydrocarbons (malodorous components) at a relatively low concentration, that is, 1/3 of the maximum fuel supply mentioned above. There is.

By controlling the amount of fuel supplied to the deodorizing equipment in this way, the overall amount of fuel supplied during scrap preheating can be reduced to about half or more compared to the conventional method, which maintains a constant and maximum amount at all times. Needless to say, as shown by the solid line in the figure, the total hydrocarbon concentration at the outlet of the deodorizing device can be sufficiently reduced, and the malodorous components can be sufficiently combusted, resulting in the scrap being preheated. It can deodorize exhaust gas.

<Effects of the Invention> As explained above, the present invention has the effect that the amount of fuel supplied to the deodorizing device during scrap preheating can be significantly reduced, and therefore energy saving can be achieved accordingly.

[Brief explanation of the drawing]

FIG. 1 is a system diagram schematically showing one implementation procedure of the present invention,
Moreover, FIG. 2 is a graph illustrating the implementation results. 11... Arc furnace, 12... Furnace lid 21...
Combustion tower, 31.32... Valve 41... Scrap preheating mechanism, 51... Deodorizing device 61... Control valve, 82... Fuel supply system 63... Control device , 71... Tara 81... Suction fan, 81...
...Dust collector patent applicant Daido Steel Co., Ltd. Agent Patent attorney Hiroshi Iriyama

Claims (1)

[Scope of Claims] 1. When preheating scrap using exhaust gas from an arc furnace and deodorizing the exhaust gas after preheating the scrap by burning it in a deodorizing device while supplying fuel, supplying fuel to the deodorizing device. A method for controlling a deodorizing device, characterized in that the amount is controlled in synchronization with an opening/closing signal of a furnace lid of an arc furnace. 2. The method of controlling a deodorizing device according to claim 1, wherein the amount of fuel supplied to the deodorizing device is maximized by a signal from opening to closing of the furnace lid of the arc furnace, and then reduced after a predetermined time by a timer.