JPS5856076B2 - Cooling water circulation system for water-cooled walls in steelmaking arc furnaces - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cooling water circulation system for a water-cooled wall in an arc furnace for steelmaking, which consumes less circulating water, provides excellent heat conduction ability to the water-cooled wall, and prevents corrosion within the circulation system. This is to prevent the occurrence of a loss of 1.

In order to improve the productivity of steelmaking arc furnaces, the power input into the furnace has recently been increased.

As the power input into the furnace increases as described above, the life of refractories on the inner wall surfaces of the furnace, such as the inner wall and ceiling of the furnace, is becoming significantly shorter.

Despite efforts to improve the quality of refractory materials, it has become impossible to fundamentally extend the lifespan of refractory materials.

Recently, as a measure to fundamentally solve these problems, metal water-cooled furnace inner walls (hereinafter referred to as water-cooled walls) have been used in place of refractories, and have achieved excellent results.

However, in order to expect sufficient effects from such water-cooled walls, a large amount of high-quality cooling water is required.

Water walls were originally used to cool the refractory from the back, but now they are commonly used completely exposed inside the furnace.

As the heat load on the water-cooled wall increases, the amount of cooling water must be increased to maintain heat balance, and cooling must be strengthened to prevent the surface temperature of the water-cooled wall from exceeding the safety limit of the metal that makes up the water-cooled wall. .

In the case of an arc furnace for steelmaking, slag or molten steel may suddenly come into contact with the inner wall of the furnace, and in this case, in order to prevent burnout of the water 1, it is necessary to keep a large amount of cooling water flowing at all times.

On the other hand, water sources are becoming increasingly scarce year by year, and many factories are unable to adopt water-cooled walls due to the supply-demand balance of water within their factories.

In addition, when a water-cooled wall is used, there is a problem in that the heat-receiving surface is prone to overheating islands if there is a water outage accident.

Therefore, an ideal cooling water circulation system would be one that consumes a small amount of high-quality cooling water and is safe even in the event of a power outage.

Here, to explain the conventional technology, the cooling water circulation device of the water cooling wall that has been used in the past is: (a) A disposable cooling water system as shown in FIG. 1A.

→A circulation system with a natural cooling reservoir as shown in Figure 1B.

g) A circulation system with a cooling function using a cooling tower as shown in Figure 1C.

03 are representative.

In FIG. 1, a indicates the furnace inner wall, b the tank, C the reservoir, and d the cooling tower.

In this case, industrial water is usually used as the cooling water, and in order to save water, Roha water is often used.

The conventional technology has the following problems.

That is, ■ Decrease in cooling function due to corrosion and limescale buildup on the cooling surface.

Industrial water contains impurities, and impurities increase with repeated circulation, and oxygen tends to dissolve in the cooling water when it comes into contact with the atmosphere.

Therefore, there is a lot of water scale deposited on the cooling surface, reducing the cooling effect and corrosion of the cooling surface side due to impurities and dissolved oxygen is unavoidable, and corrosion on the inner surface often affects the life of the water cooling wall.

This tendency is greater as the water temperature increases, so even if the water temperature is high, the amount of water is usually determined so that it does not exceed 60°C.

■Increase in required amount of cooling water.

In the case of arc furnaces for steelmaking, there is considerable variation in the heat load on the inner wall of the furnace during one cycle from tapping to the next tapping 1 even during normal operation. Direct contact may occur suddenly, resulting in a large local heat load being applied to the heat receiving surface.

However, even in this case, the heat receiving surface must be sufficiently safe.

If the heat load on the water-cooled wall is high and the temperature rise of the cooling water increases, water scale buildup on the cooling surface and corrosion of the cooling surface will increase. In order to maintain safe and stable operation of the reactor to prevent burnout, it is necessary to constantly supply a large amount of cooling water.

Therefore, when there is a restriction on the amount of cooling water, the prior art has considerable limitations on the full adoption of safe and long-life water cooling walls.

O Measures against power outage accidents.

Generally, cooling water circulation systems are often provided with an emergency elevated water tank as a countermeasure against power outages.

However, in the case of the water-cooled furnace wall of an arc furnace, the amount of water used is extremely large, and the water supply function can only be maintained for a short period of time, making it uneconomical.

Furthermore, even if the water pump's power source is switched to the emergency power source during a power outage, if the switching time is long, the heat receiving surface of the water cooling wall may be damaged by overheating.

Conventionally, the cooling water pump is often driven by a diesel generator during a power outage, but in this case, immediately after a power outage, the diesel generator starts for 5 minutes or 1
It takes about 0 minutes.

The following functions are required for a water cooling wall cooling water circulation system for a steelmaking arc furnace.

(I) Circulation of cooling water is performed stably even when the furnace body is tilted or the furnace cover is rotated.

For this reason, rubber hoses can be used for moving parts.

(II) Possibility of flexible arrangement of cooling water passages in water cooling walls.

Therefore, even if there is a difference in the resistance of the cooling channel, there is no difference in the amount of water.

(II [) High-pressure vessels and boilers → Not subject to removal regulations, and safe even without special techniques for handling.

■There is little corrosion on the cooling surface due to cooling water, and there is no adhesion of scale or other deposits.

(V) It must be able to adequately respond to fluctuations in heat load, have a large amount of heat removed, and be safe even against excessive heat loads such as contact with molten steel.

(VI) The amount of water should be as small as possible.

(■) Must be safe against power outages and pump failures.

In the conventional technology, in order to satisfy the above conditions α), (2), and (■), a method is adopted in which water is circulated and cooled using a pump. There is a problem with economics as it requires a large amount of.

Request (b) cannot be satisfied.

The present invention was made in view of these points, and it consumes less circulating water, provides water cooling walls with excellent heat transfer ability,
This system provides a cooling water circulation system that prevents corrosion and cracks from occurring in the circulation system, and includes a steam/water separation drum whose upper end is open to the atmosphere, a regular system pipe connected to the air/water separation drum at its upper end, and an emergency system pipe. A system pipe, a water riser pipe whose upper end opens into the air layer in the air-water separation drum, a circulating water cooler, a check valve, a circulation pump, and a water supply connected in series between the normal system pipe and the water riser pipe. A header, a throttle section, a water cooling wall group, an outlet header, an air nozzle, a water supply water level transmitter and a canned water level transmitter attached to the steam/water separation drum, a water supply main pipe that normally supplies water to the steam/water separation drum; Cooling of a water-cooled wall in an arc furnace for steelmaking, characterized by having a spray nozzle, an emergency water supply system pipe for emergency water supply, a can water saving and can water control valve for discharging excess water from the steam/water separation drum. The gist is water circulation equipment.

Next, an embodiment of the present invention will be described with reference to FIG. 2. Reference numeral 1 denotes a steam/water separation drum, in which relatively high temperature canned water 2 is placed.

The upper ends of the regular system pipe 3 and the emergency system pipe 4 are connected to the bottom of the steam/water separation drum 1, and the upper end of the riser pipe 5 is opened above the canned water 2 of the steam/water separation drum 1. There is.

Between the regular system pipe 3 and the rising water pipe 5, there are two circulating water coolers 6 connected in parallel, a check valve 7, and two circulating water coolers 6 connected in parallel.
Three circulation pumps 8, a flexible piping section 9, a water supply header 10, a throttle section 11, a water cooling wall group 12, an outlet header 13, a flexible piping section 14, and an air nozzle 15 are connected in series.

The reason why two circulating water coolers 6 and two circulating pumps 8 are connected in parallel is for maintenance purposes, and the water cooling wall group 12 is for increasing heat exchange efficiency.

The emergency system pipe 4 is connected to the outlet side of the circulation pump 8 via a check valve 16.

A stack 17 whose upper end is open is formed on the upper part of the steam/water separation drum 1, and a roof 18 is provided above the stack 17.

A spray nozzle 20 connected to the tip of the water supply pipe 19 is disposed inside the stack 17 .

An emergency water supply system pipe 21 whose tip is opened into the canned water 2 in the steam/water separation drum 1 is connected to this water supply source pipe 19 .

A spray control valve 22 is installed in the main water supply pipe 19 and is turned off, and an emergency water supply control valve 23 is installed in the emergency water supply system pipe 21 and disconnected.

These control valves 22 and 23 are controlled to open and close by a water supply controller 25 that receives a signal from a water supply water level transmitter 24 attached to the steam/water separation drum 1.

A water level transmitter 26 for canned water is further attached to the steam/water separation drum 1, and the canned water control valve 29 is controlled to open and close via a canned water controller 27, so that the upper end thereof is opened into the canned water 2. Canned water flows from the canned water pipe 28.

This device thus constructed operates as follows.

Relatively high-temperature canned water 2 in the air-water separation drum 1, which is located at a higher location than the water cooling wall group 12 and is open to the atmosphere, is transferred to a circulating water cooler 6 by a circulating pump 8 installed in a regular system pipe 3. , from the water supply header 10 via the check valve 7 to the water cooling wall group 12
It receives heat from the iron and reaches a high temperature, and is circulated from the outlet header 13 through the riser pipe 5 to the original steam-water separation drum 1.

In this case, if the heat load is high when passing through the water cooling wall group 12, the circulating water will partially evaporate and circulate with steam.

The circulating water cooler 6 is used for the purpose of lowering the temperature of relatively high-temperature water in the air-water separation drum 1, or in some cases saturated water, as much as possible to supply water to the water cooling wall group 12 at a low temperature to reduce the amount of high-quality make-up water. be exposed.

Note that the cooling water to the circulating water cooler 6 is supplied to the water cooling wall group 12.
The plan is to use low-quality industrial water, return water, seawater, etc. that cannot be used as circulating water.

Since the temperature of the circulating water is relatively high, at a level of 70 to 100° C. (saturation temperature), the cooling area of the circulating water cooler 6 may be relatively small.

The check valve 16 provided in the emergency system pipe 4 prevents pressurized circulating water from the regular system pipe 3 from flowing into the emergency system pipe 4, and the check valve 7 prevents pressurized circulating water from flowing into the emergency system pipe 4 during a power outage. This prevents circulating water from the emergency system pipe 4 from flowing into the regular system pipe 3.

Further, the flexible piping sections 9 and 14 in the piping are provided with consideration given to enabling tilting of the furnace body and rotation of the furnace lid, which are necessary for a steel-making arc furnace.

Since the flexible piping section 9.14 is provided in this way, care is taken to keep the pressure within the system as low as possible.

The throttle section 11 is provided to provide sufficient additional resistance to piping resistance and equalize the flow rate.

When the circulating water has a high heat load, a part of it becomes steam when it passes through the water cooling wall group 12, but it is separated from water in the steam/water separation drum 1 and released into the atmosphere from the stack 17. .

Therefore, the level of the canned water 2 in the steam/water separation drum 1 gradually decreases.

Makeup water to supplement this is provided from a spray nozzle 20 provided within the stack 17.

The purpose of this spray replenishment is to condense the steam dissipated into the atmosphere as much as possible on the way to minimize the amount of makeup water, and to preheat the feed water for deaeration.

The water level in the steam/water separation drum 1 is detected by a water supply water level transmitter 24, and is supplied from a water supply main pipe 19 via a spray nozzle 20 under a command from a water supply controller 25.

When drinking water is rapidly decreasing, water is replenished from the emergency water system pipe 21 by the emergency water supply control valve 23.

Further, when the water level rises abnormally, the excess water is drained to the outside by the canned water control valve 29.

The roof 18 prevents rainwater from entering the air/water separation drum**1 from the outside.

As an emergency measure, in case the circulation pump 8 stops, compressed air is introduced into the air nozzle 15 provided at the bottom of the water riser pipe 5, and the water riser pipe 5 is used as an air lift pump to circulate the cooling water. This is to prevent damage to the water cooling wall group 12.

At this time, most of the circulating water descends through the emergency system pipe 4, which has less resistance.

The performance of this device is that the amount of heat removed from the circulating water cooler 6 is 100'.
When l:10' KCal/h, the results are as shown in the following table.

As mentioned above, the present invention consumes less circulating water, requires less water in the circulating water cooler for cooling the circulating water, provides the water cooling wall with excellent heat transfer ability, and prevents corrosion within the circulation system. No sagging occurs.

Furthermore, since the steam/water separation drum is open to the atmosphere, the pressure in the circulation system is low, allowing safe circulation to the moving parts.

Furthermore, the circulation system can be freely arranged, the flow rate to each circulating water system is uniform, and there is an effect of being safe against pump accidents and power outage accidents.

[Brief explanation of drawings]

FIGS. 1A, B, and C are explanatory views showing a conventional water-cooled wall cooling water circulation system, and FIG. 2 is an explanatory view showing the configuration of the water-cooled wall cooling water circulation system in an arc furnace for steelmaking according to the present invention. 1... Air-water separation drum, 3... Regular system pipe, 4...
・Emergency system pipe, 5... Water riser pipe, 6... Circulating water cooler, 7.16... Check valve, 8... Circulating pump, 9,
14...Flexible piping section, 10...Water supply header, 11.
... Throttle part, 12... Water cooling wall group, 13... Outlet header, 15... Air nozzle, 19... Water supply source pipe, 20
... Spray nozzle, 21 ... Emergency water supply system pipe, 2
4... Water level transmitter for water supply, 26... Water level transmitter for canned water, 28... Pipe for canned water, 29... Control valve for canned water.

Claims (1)

[Claims] 1. A steam and water separation drum whose upper end is open to the atmosphere, a regular system pipe and an emergency system pipe whose upper ends are connected to the steam and water separation drum, and a riser pipe whose upper end is opened into the air layer in the steam and water separation drum.
A circulating water cooler, a check valve, a circulation pump, a water supply header, a throttle section, a water cooling wall group, an outlet header, an air nozzle, and an air nozzle connected in series between the regular system pipe and the water riser pipe, attached to the air-water separation drum. a water level transmitter for water supply and a water level transmitter for canned water, a main water supply pipe and spray nozzle for normally supplying water to the air/water separation drum, an emergency water supply system pipe, and a canned water for discharging excess water from the air/water separation drum. Control valves for utility pipes and canned water,
A cooling water circulation device for a water-cooled wall in a steelmaking arc furnace, characterized by having the following features: