JPS5925935B2 - Continuous heat treatment equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a continuous heat treatment apparatus that uses fuel as a heat source and recovers the heat possessed by a heat-treated object that has undergone heat treatment.

Continuous heat treatment equipment is a device that completes heat treatment by passing the object to be treated through a furnace that has a temperature distribution according to the heat treatment conditions in its length direction, and has higher thermal efficiency than batch type equipment. It has excellent productivity and is widely used in various fields.

Since this apparatus has high thermal efficiency, a large proportion of the heat input from the heat source is retained and taken out as sensible heat by the high-temperature processed material that has completed the heat treatment.

The amount of heat taken out by the object to be processed is large because the heating temperature is high in the ceramics and steel industries.

However, many large-capacity devices of this type still use fuel as their heat source due to the cost of heat.

Conventionally, the heat emitted from this continuous heat treatment equipment has been recovered from the exhaust gas, but the amount of heat retained in the material to be treated has not been sufficiently recovered, and for thermoeconomic reasons, it is necessary to release the high-temperature material into the air. In order to cool down, the inside of the factory became hot, causing problems such as interfering with the next process.

SUMMARY OF THE INVENTION An object of the present invention is to provide a continuous heat treatment apparatus using fuel as a heat source, which recovers at a high yield the amount of heat possessed by a material to be treated that has undergone heat treatment.

In continuous heat treatment equipment, the most common method for recovering the amount of heat held by the processed material after processing is to provide a heat exchange chamber behind the final heating chamber of this equipment, where the material to be processed is exchanged with air, etc. In the case where heat is exchanged by direct contact with a heat medium and fuel is used as a heat source, air is used as the heat medium and used as combustion air.

However, in this type of processing equipment, the outlet of the material to be processed in the final heating chamber has a large cross section so that the material with the largest cross section can pass through without any problem, and the area normally occupied by the material to be processed relative to this opening is small. Even if a means to reduce the opening area by installing a vertically adjustable door or the like is used, the opening still has a large cross section.

Through this opening, a large amount of combustion gas is discharged into the atmosphere either directly through the hood or via a heat exchanger or the like.

Even if a heat exchange chamber is provided in this state, due to the minute pressure difference between this heat exchange chamber and the final heating chamber and the density difference of the gas in the compartment,
Through this large-area opening, the combustion product gas from the final heating chamber flows into the heat exchange chamber or the air from the heat exchange chamber flows into the final heating chamber in large quantities.

In the former case, the extracted air contains a large amount of combustion gas, and the amount fluctuates, so stable combustion cannot be performed and it cannot be used as combustion air.

In the latter case, the temperature distribution in the final heating chamber is disturbed by the inflow of low-temperature air, which greatly affects the function of the heat treatment apparatus.

It is theoretically possible to reduce the pressure difference between compartments as a way to reduce the inflow and outflow between compartments.
This pressure difference is so small that it is very difficult to detect and control it with a slight time delay.

Furthermore, as a shielding means for reactor air, etc., methods have been known in which hydrodynamically shielding gas curtains, frame curtains, mechanically shielding ribbons, chains, heat-resistant fibrous materials, etc. are suspended in a curtain-like manner.

However, with gas curtains, it is necessary to blow out high-temperature gas so as not to affect the temperature of the final heating chamber, and there are problems with the supply of this gas and the equipment that handles it.

Also, flame curtains cannot be used because they require fuel and reheat the material to be treated.

Furthermore, mechanical methods constantly slide against the treated material at high temperatures, are easily damaged, and are difficult to maintain.

The present invention provides a heat exchange chamber covered with a shield having an opening that allows passage of the material to be treated at the rear of the heating chamber, and the material to be treated is transported after being heated in this heat exchange chamber. The mixture ratio of the air and the combustion gas is maintained constant by detecting the concentration of a specific component in the mixed gas of the air heat exchanged from the material and the combustion gas flowing into the heat exchange chamber from the heating chamber. It is something that extracts air.

That is, the present invention prevents fluctuations in oxygen concentration, which is a condition for combustion air that can stably and completely burn, and recovers the amount of heat held by the material to be treated to obtain high-temperature air.
Thus, difficult direct gas shielding between the heating chamber and the heat exchange chamber is avoided, and some gas flow between the compartments is allowed.

In order to realize highly efficient combustion by reducing the proportion of combustion gas mixed into the heat-recovered air, this air is forced into the heat exchange chamber, and the pressure inside the heating chamber is increased. This is to reduce the flow rate of the combustion product gas flowing into the chamber as a slight positive pressure that opposes the pressure.

Next, the present invention will be explained with examples.

The figure is a sectional view of a continuous annealing apparatus for steel materials to which the present invention is applied.

The steel material 1 to be processed is transferred to the conveyor roller 3 on the entrance roller table 2.
They are then lined up and supplied using a crane or the like.

Steel materials with the same grain conditions are processed together regardless of size and shape.

This steel material is moved at low speed in the direction of arrow 1 by the rotation of the conveyance roller 3 through the heating chamber 4 and onto the take-out table 9.

A plurality of oil burners and burner tiles 5 are installed in the upper and lower parts of the material to be treated 1 on both the left and right walls of the heating chamber 4, and these burners burn air and combustion generated gas that have become high in temperature through heat exchange, which will be described later. The air-fuel mixture is supplied from a pipe 16 that has been heat-insulated, and is controlled to have a predetermined temperature distribution by a temperature detection means (not shown).

The heating chamber is divided into multiple sections to enable complex temperature distribution curves.

The combustion generated gas generated in each heating chamber changes depending on the combustion state at that time, but flows roughly to the front or rear of the furnace as shown by the arrow, and finally passes through the hoods 7 and 7' to the chimneys 8 and 8'.
It is finally released into the atmosphere through the final heating chamber 4.
A part of the combustion generated gas discharged backward from -6 is indicated by the arrow 6.
′, it also flows into the heat exchange chamber.

By passing through the heating chamber 4 which has a set temperature distribution, the material 1 to be treated is heated to a predetermined heat pattern, and then exits onto the carry-out table 9 and is carried out to the next process by a carry-out device (not shown). .

The heat exchange chamber 12 is located in the hood 7' behind the final heating chamber 4-6.
A stationary shield 10-1 having an opening adjacent to it that allows the material to be processed 1 to pass through, and a fixed shield 10-1 that runs in the front-rear direction with wheels on a track (not shown) installed on the unloading table 9 with a small gap between the shield and the shield. It is covered with a movable shield 10-2.

The rear end of the movable shield 10-2 is supplied with compressed air from a plurality of compressed air sources 15, and is connected to a blower 13 (described later) using solenoid valves M and V.
A venturi injector 11 is controlled by the output of oxygen concentration battery type gas analyzers G and A that detect the oxygen concentration in the gas sampled from the discharge side of the venturi injector 11, which is operated by compressed air supplied through a flexible rubber hose 17. It is installed in a position that allows the material to be treated 1 to pass through the lower part in the forward and downward directions.

Further, a main pipe 16 for supplying combustion air to the burner is opened above the front part of the fixed shield 10-1, and a pipe 14 is connected to an inlet of a combustion air blower 13 whose discharge port is connected to the main pipe 16.

Both shields are made of steel plate and lined with heat insulating material, making them airtight.

The venturi injector 11 draws a large amount of air from the rear of the heat exchange chamber by ejecting compressed air, and injects it onto the heat-treated treated material at the outlet of the heat exchange chamber 12 to remove the heat and cool it. The temperature of this air is increased by heat exchange, and the inside of the heat exchange chamber 12 is brought into a slight positive pressure to oppose the slight positive pressure in the heating chamber 4-6.

A part of the induced and injected air escapes as shown by the arrow 20 due to the positive pressure in the heat exchange chamber 12, but most of it flows in the opposite direction to the conveyance direction of the material to be treated 1, resulting in so-called countercurrent heat exchange and direct contact. The heat is exchanged with high efficiency to reach a high temperature, which reaches the front part of the heat exchange chamber 12.

Even though the temperature has increased, there is a density difference between the gases in this section and the heating chamber 4-6 due to the temperature difference, and at the lower part of the hood 7, which is the boundary between the compartments, a part of the heat-exchanged air flows into the heating chamber. As described above, a part of the combustion generated gas in the heating chamber 4-6 enters the heat exchange chamber 12 at the upper part.

Therefore, the air sucked and extracted from the pipe 14 contains a portion of the combustion generated gas that has entered from the heating chamber 4-6.

The aforementioned control system increases the number of operating venturi injectors when the oxygen concentration in the suction bleed air becomes low, thus increasing the amount of induced air and reducing the amount of intruding combustion product gas, thereby reducing the oxygen concentration. It operates to rise.

Therefore, the air-fuel mixture extracted from the heat exchange chamber 12 and supplied to the burner is always within a certain range of components, and stable complete combustion can be continued.

By selecting the oxygen concentration of the oxtail, the amount of air entering the heating chamber 4-6 from the heat exchange chamber 12 can be controlled, and the temperature distribution within the heating chamber 4-6 is not adversely affected. I can do it.

In this example, the average gas temperature on the blower discharge side was 300°C, and a fuel reduction rate of about 5% could be achieved.

In this example, a heat exchange chamber is provided on a limited transfer table 9 of an existing continuous heat treatment apparatus, and the shield is divided into two and has an expandable structure, but the movement of the movable shield due to expansion and contraction is The heat exchange room continues its function during the period and during the shortening period.

If the space is not limited, the shield may be fixed.

In addition, this embodiment adopts a venturi injector as a forced ventilation means, making it more compact and increasing the length of the effective heat exchange chamber, preventing interference with the conveying device or the material to be processed, and ensuring high reliability even in poor environments. We were able to.

Of course, other low-pressure pressure feeding means may be employed, and the control system may not only control the amount of air blown, but may also include a constant air amount blowing valve and control the amount of escape air.

That is, any material that controls the ventilation effect may be used.

The present invention is not necessarily limited to forced ventilation.

In this embodiment, in order to prevent the flow state of the combustion gas in the heating chamber 4 from fluctuating widely between before and after the new heat exchange chamber is installed, a method was adopted in which the amount of air sucked from the heat exchange chamber was supplemented by forced ventilation. It goes without saying that, for example, a valve 18 may be provided in the chimney 8', the degree of opening of the valve 18 may be controlled by gas analyzers G and A, and ventilation may be carried out by the suction force of the chimney.

It goes without saying that the high-temperature air whose heat is recovered in the present invention can be used for other purposes.

As described above, the present invention makes it possible to recover the sensible heat of the processed material after heat treatment with high efficiency, which not only improves thermal efficiency but also improves secondary processes such as handling in the next process and preventing overheating in the factory. effect was also possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a continuous heat treatment apparatus for steel materials to which the present invention is applied. 1: Processed material, 4: Heating chamber, 5: Burner tile, 6.6
': Arrow indicating gas flow, 101.10-2: Shielding body,
11: Venturi injector, 12: Heat exchange chamber, 1
3: Blower, 14, 16: Piping, G, A: Analyzer, M,
V: Solenoid valve.

Claims (1)

[Scope of Claims] 1. In a continuous heat treatment device that heats a material to be heated by burning fuel, a heat exchange chamber covered with a shield having an opening at the rear of the heating chamber that allows the material to pass through. is provided, and the specific components in the mixed gas with the air heat-exchanged from the processed material that has been conveyed after completing the heat treatment in this heat exchange chamber and the combustion generated gas that has flowed into the heat exchange chamber from the heating chamber. A continuous heat treatment apparatus characterized in that the mixture ratio of the air and combustion generated gas is kept constant and air is extracted by detecting the concentration. 2. The continuous heat treatment according to claim 1, wherein the air to be heat exchanged in the heat exchange chamber is supplied by forced ventilation, and the forced ventilation effect is controlled by the concentration of a specific component in the mixed gas. Device.