JPH01127645A - Method for treating closed type alloy electric furnace equipment at stopping power - Google Patents

Abstract

PURPOSE:To prevent explosion accident after stopping supply of power to the electric furnace by introducing non-combustible gas from connecting part of an electric furnace with a cooling and dust collecting equipment, to diluting stagnant combustible gas in equipment, and discharging it to outside. CONSTITUTION:Just after stopping supply of the power to the electric furnace 1, the non-combustible gas of N2 gas, etc., is blown from non-combustible gas introducing pipe 16 arranged in the connecting part of the electric furnace 1 with the waste gas cooling and dust collecting equipment. By this gas blowing, CO gas component in the waste from a second chimney 13 is reduced and atmosphere in the waste gas cooling and dust collecting equipment is come to out of the explosion dangerous range. Successively, an inspection hole 14 for ignition being apart from gas off-take part 3 in the electric furnace 1 is opened, and after igniting, a damper 11 for adjusting gas flow rate is fully opened to introduce the air, and the remained gas in the electric furnace 1 is burnt. After introducing the combustion waste gas cooling and dust collecting equipment, the waste gas is diffused from the second chimney 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for safely processing residual gas in an electric furnace when a closed type ferroalloy electric furnace is positively energized, and in particular, a method for igniting and burning the residual gas. This article relates to a method to eliminate the danger of explosion when processing.

[Prior Art] A large amount of high-temperature flammable gas is generated from an electric furnace for manufacturing ferroalloy.1. Dispersing this into the atmosphere as it is causes problems such as loss of valuable substances, release of thermal energy, and generation of air pollution. For this reason, consideration has been given to making the electric furnace a closed type, and now the majority of electric furnaces in Japan are of the closed type.

The components of the combustible gas recovered using the closed system vary depending on the ferroalloy for which it is manufactured, but generally the main component is CO, with a small amount of N2, CO2, or even a small amount of O. YaN
It is useful as a fuel or raw material for synthetic chemical industry. However, since it is ejected from inside the electric furnace, it contains a large amount of dust and is at a high temperature, so if it is desired to retain it in a gas holder as a useful gas, it is necessary to perform dust removal and cooling treatment. Therefore, for example, they are cooled by water spraying and the recovered heat is used as various heat sources, and gas processing equipment is installed to remove dust.

In Fig. 1, the portion excluding the inlet pipe indicated by 16 is an explanatory diagram showing conventional processing equipment, and the electric furnace gas generated by the steady operation of the electric furnace 1 is transferred to the gas offtake formed in the electric furnace M2. The gas is sent through section 3 to the gas processing equipment on the right side of the drawing. At that time, an inspection hole 4 formed in the electric furnace cover 2
(14 locations in the figure) and a water seal damper 6 leading to the first chimney 5 above the furnace are closed to prevent outside air from entering.

The high-temperature, dust-containing gas entering the gas processing equipment is first cooled in a pre-cooling tower 7 and subjected to preliminary dust removal, and then further dust removed in a Tizen washer 8. Next, water droplets are removed by a water separator 9, and the pressure is increased by a booster roller 10. Since the amount of gas generated in the electric furnace 1 usually varies depending on the operating conditions, an electric damper 11 is provided to adjust the gas feed amount corresponding to the amount of gas generated. As a result of the gas analysis performed, if the gas is suitable for storage in the gas holder, the U-shaped water seal tube 15
When the gas is found to be unsuitable for storage, the three-way switching valve 12 is activated and the gas is released into the atmosphere from the second chimney 13 with or without appropriate gas treatment. . If the amount of exhaust gas from the electric furnace 2 increases temporarily while the water seal damper 6 is closed, the load in the gas processing equipment will increase, so in order to alleviate this, the Ascania damper 17 is opened and the recycling pipe is opened. Increase the amount of recycled gas in 18.

In the above-mentioned steady-state operation, the operation may be interrupted for various reasons, such as when it is time for periodic repairs to the electric furnace 1 or related equipment, or when it is desired to observe the inside of the electric furnace 1. There are times when you have to. In such an interruption, the power supply to the electric furnace is stopped, but as this stops gas generation within the furnace, the problem becomes how to deal with the flammable gas remaining in the space within the furnace lid. If the next work is started without treatment, there is a possibility that air will flow into each space inside the furnace lid depending on the pressure balance with the atmospheric pressure. Furthermore, if the furnace lid is opened for some reason, air naturally flows in and mixes with the flammable gas inside the furnace lid. On the other hand, since the temperature inside the furnace is high and there is an ignition source, the flammable gas mixed with the atmosphere burns, causing an explosion depending on the mixing ratio. For this reason, it is necessary to safely dispose of the residual gas on the furnace lid when the power is cut off, and the dust emitted from this processing must be disposed of by some means from the perspective of preventing air pollution. It won't happen. The inside of this furnace lid is dome-shaped and has a complicated structure divided into several parts, so it is difficult to equate the residual gas composition inside the furnace lid with the gas composition in the center of the furnace. There is a problem.

Conventionally, the following two methods have been adopted from the perspective of disaster prevention.

■The exhaust gas introduction part to the gas processing equipment is shut off from the electric furnace by means such as a water counter, and measures are taken to prevent atmospheric air and high-temperature furnace gas from entering the gas processing equipment. Next, inert gas or steam is introduced into the electric furnace lid while taking care to prevent the inside of the electric furnace lid from becoming negative pressure with respect to outside air pressure, thereby bringing the composition of the gas inside the furnace lid out of the flammable range.

■A method of actively burning residual flammable gas within the furnace lid.

[Problems to be solved by the invention] Among the above methods, method (①) requires time to elapse until the gas inside the furnace lid is out of the flammable range, and it is also necessary to measure the gas components and concentration within the furnace lid. be. However, as mentioned above, the structure inside the furnace lid is complex and divided into many spaces, so it is impossible to check whether all parts are outside the flammable range, and it is impossible to do so during actual operation. The reality is that in order to ensure safety, purging is carried out more than necessary and sufficient.

On the other hand, when carrying out method (2), first, the inside of the electric furnace is shut off using the same method as in (2), and then the electric furnace is positively energized. Next, while controlling the opening degree of the water seal damper 6, the ignition inspection hole 14 furthest from the gas off-take part 3 is opened so that the pressure inside the furnace does not become a negative pressure, that is, it is higher than the outside pressure. The gas that has been released outside the furnace is ignited using a pilot flame. Thereafter, by increasing the opening degree of the water seal damper 6 to adjust the pressure inside the furnace lid to be more negative than the outside pressure, the gas being ignited and burned is drawn into the furnace together with the atmosphere, and the gas inside the furnace lid is combusted. This method requires more skill than method ■, but
Since the processing time is short and the gas in the furnace lid burns to a safe level, it is also excellent in terms of safety, and method (2) is becoming more and more commonly used for crotch meat. In this case, introducing the flue gas into the gas treatment equipment according to the gas line shown in Figure 1 may cause an explosion accident due to the mixing of flammable gas in the treatment equipment and oxygen in the flue gas. It is released into the atmosphere from the first chimney 5 shown in the figure. However, since the exhaust gas at this time is often not passed through a dedicated dust collector, it still contains a large amount of dust, and brown or white exhaust gas is released into the atmosphere for several tens of minutes.

As described above, the conventional methods cannot be said to be sufficient from the viewpoints of safety and environmental friendliness.

[Means for Solving the Problems] The inventors of the present invention have focused on the above-mentioned circumstances, and the purpose of the present inventors is to provide a method that can perform electric furnace positive electric work in a manner that satisfies both safety and environmental hygiene. conducted research. That is, the present invention provides, in a case where an exhaust gas cooling/dust removal equipment is connected to a closed type ferroalloy electric furnace, after stopping the power supply to the electric furnace, from the connecting part of the electric furnace and the exhaust gas cooling/dust removal equipment A non-combustible gas is introduced to remove the atmosphere inside the exhaust gas cooling/dust removal equipment from an explosion danger range, and then the gas in the electric furnace is ignited and combusted, and the combustion exhaust gas is released outside the system via the exhaust gas cooling/dust removal equipment. The aim is to implement the project in the future.

[Function] In the present invention, in view of the fact that the method (2) described in the conventional example has a problem in the treatment after the combustion of the gas in the furnace lid (white smoke discharge from the first chimney 5), the present invention provides exhaust gas cooling and The basic configuration is to purge combustible gas in gas piping in dust removal equipment with non-combustible gas in advance.

In other words, there is a combustible gas rich in CO and also containing H2 remaining in the gas pipe, and if the mixed gas of the high-temperature gas and the atmosphere generated in the method ① is supplied as it is into the gas pipe. It was feared that these would mix to form a gas composition in the explosion danger zone, and that it would explode using the high-temperature exhaust gas as a heat source. However, if the method of the present invention is adopted, most of the combustible gas in the gas pipe is purged with non-combustible gas, and the above situation can be avoided. Therefore, even if the combustion gas from the furnace lid is introduced into the exhaust gas cooling/dust removal equipment together with the atmosphere, it will not cause an explosion, and the cooling and dust removal will be carried out within the equipment. However, the environmental conservation problem of brown to white smoke being emitted has disappeared. The above-mentioned non-combustible gas used in the present invention is typically nitrogen gas, but it is also possible to use combustion exhaust gas generated from other combustion devices. As mentioned above, the main point of the present invention is to introduce non-combustible gas from the joint between the electric furnace and the exhaust gas cooling/dust removal equipment to safely or partially purge the combustible gas in the exhaust gas cooling/dust removal equipment to create an explosive atmosphere. Because it exists in preventing the formation of
The individual configurations of the electric furnace and exhaust gas cooling/dust removal equipment do not matter, and the composition of the gas after the purging is not absolutely regulated.

The present invention employs the above-mentioned purging method using non-combustible gas, but compared to the method (2) explained in the prior art section, the method (2) uses the inside of the furnace lid, which is a place that is extremely difficult to purge. In contrast to forced, incomplete, and uneconomical purging, this method uses pipe purging, which is a very reliable and economical method. , which is a less versatile method that requires excessive purging beyond the necessary and sufficient amount, whereas the present invention allows only the minimum amount of purging to be performed without requiring special skill. Although it can equally be called a purge method, it can be said that the present invention is far superior in terms of its technical content and effects.

[Example 1] A non-combustible gas introduction pipe 16 shown by a chain line was attached to the outlet side gas pipe (gas off-take section 3) of the electric furnace 1 in FIG. 1 to form an apparatus for implementing the present invention.

Immediately after stopping power supply to the electric furnace 1, about 1500 Nm3/Hr of nitrogen gas was blown from the non-combustible gas introduction pipe 16. The exhaust gas composition measured near the second chimney 13 immediately before nitrogen gas injection (equivalent to the gas composition in the electric furnace 1) was CO2: 3%, H2: 1.5%, CO2: 25%, and other 20%.
．． 5%, but as we continued to measure the gas composition at the same point, the CO acid component began to decrease 5 minutes after nitrogen gas was blown in, and the CO acid component decreased to 12% after 10 minutes. Since the flammability range of Co gas is generally considered to be 12.5% or more, the above measured value indicates that the danger of explosion has been avoided. Therefore, the gas offtake section 3 in the electric furnace 1
The ignition inspection hole 14 furthest from the furnace was opened, and after ignition using a pilot flame, the gas flow rate adjustment damper 11 was fully opened to introduce atmospheric air 1, and the residual gas in the electric furnace 1 was combusted. The combustion exhaust gas in the electric furnace 1 was introduced into the exhaust gas cooling/dust removal equipment, and after being subjected to cooling and dust removal treatment, it was released from the second chimney 13. The dust concentration of conventional exhaust gas (exhaust gas from the first chimney 5 in method ①) in which such measures of the present invention were not taken was 25.3 g/Nm', but by implementing the method of the present invention, the dust concentration was reduced to 0.056 g/Nm'. g/Nm3.

[Effects of the Invention] The present invention is configured as described above, and since the combustible gas accumulated in the exhaust gas cooling/dust removal equipment is diluted by the non-combustible gas to below the explosion danger area, the remaining combustible gas on the lid of the electric furnace is reduced. Even if a mixed gas of high-temperature combustion exhaust gas generated when gas is combusted and the atmosphere is introduced into the exhaust gas cooling/dust removal equipment, an explosion will not occur in the equipment. In addition, the operating procedure is simplified compared to the conventional example, and it can be easily carried out without requiring any skill.In addition, the combustion exhaust gas remaining on the furnace cover can be cooled and dust removed, so it is possible to reduce the environmental impact due to atmospheric dissipation. Concerns about deterioration have also been resolved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an example of the arrangement of an electric furnace and exhaust gas cooling/dust removal equipment. 1... Electric furnace 2... Furnace lid 3... Gas off-take part 4... Inspection hole 5... First chimney
6... Water seal damper 7... Precooling tower 8
... Tizen washer 9 ... Moisture unit l
O... Booster blower 11... Gas flow rate adjustment damper 12... Three-way switching valve 13... Second chimney 14
...Ignition inspection hole 15...U-shaped water seal tube 16
...Non-combustible gas introduction pipe

Claims (1)

[Claims] In a power outage treatment method for closed-type ferroalloy electric equipment, which consists of an electric furnace for ferroalloy melting and exhaust gas cooling and dust removal equipment,
After stopping the power supply to the electric furnace, non-combustible gas is introduced from the connection between the electric furnace and the exhaust gas cooling/dust removal equipment to remove the atmosphere inside the exhaust gas cooling/dust removal equipment from the explosion danger range, and then the electric furnace is turned off. A method for processing a closed type ferroalloy electric furnace equipment during a power outage, characterized in that internal gas is ignited and burned, and the combustion exhaust gas is discharged outside the system via the exhaust gas cooling and dust removal equipment.