KR810000842B1 - Apparatus for use of waste-heating in annealing acid cleaning process of metal strip - Google Patents

Abstract

The apparatus for use of waste-heating in annealing acid cleaning process of metal strip is made up of the continuous annealing furnace(2), the preheat treatment zone(6) and the exhausted gas pipe(9). The heat exchanger(12,13) is equipped with the waste heat boiler(10) being supplied from the exhausted gas pipe, the supply system having acid rinsing apparatus(3), the washing apparatus(4) and the drying apparatus(5).

Description

Waste heat utilization device in annealing and pickling process of metal strip

1 is a cross-sectional side view of a continuous annealing furnace of a conventional stainless strip.

2 is a side cross-sectional view of a continuous annealing furnace used in the annealing and pickling process of the present invention.

3 is a schematic illustration of the waste gas heat using apparatus in the annealing pickling process of the present invention.

4 is a schematic explanatory diagram showing a modification of FIG.

The present invention relates to an apparatus for utilizing waste gas heat in an AP line comprising a stainless strip continuous annealing furnace and its subsequent equipment, namely an pickling device, a water washing device, a drying device, and the like. .

In the conventional stainless strip continuous annealing furnace (a), as shown in FIG. 1, the exhaust gas port (c) is installed on the ceiling of the first section to heat the strip (w) traveling by the heating device (b). The combustion gas generated in the soil was discharged from the exhaust gas port c to the outside via a waste gas pipe (not shown).

However, this waste gas is about 1150 ° C near the exhaust gas port, and not only is it damaged by the waste gas pipe or the heat exchanger of the waste gas, but it is also a great loss in terms of thermal efficiency to discharge the high temperature waste gas as it is.

Here, the thermal efficiency of the stainless strip continuous annealing furnace shows that when the heat load of the battle is 100%, about 38% of the heat is provided to the material, about 3% is the furnace wall loss, and about 50%. Is discharged outside the furnace as waste gas.

That is, in the conventional stainless strip continuous annealing furnace, it is a phenomenon that about half or more of calorie | heat amount under combat does not contribute to heating of a material, and is a phenomenon.

The present invention attempts to utilize waste gas extremely effectively in the light of such a conventional defect and a significant rise in energy production costs in recent years.

That is, according to the present invention, a preheating zone having a smaller cross section in the furnace than that of the annealing furnace is provided at the front of the first section of the stainless strip continuous annealing furnace, and is discharged from the upper portion of the first section. The waste gas is introduced into the preheating zone to preheat the material, and the waste gas from the waste gas pipe installed in front of the preheating stage is introduced into the waste heat boiler to heat the waste heat boiler and then discharge it to the outside. Steam generated by heating of the pickling liquid used in the pickling unit installed behind the continuous annealing furnace, or the hot water used in the washing unit, or used in the drying unit It is used for heating of dry air, etc., respectively.

Next, the present invention will be described in detail with reference to FIGS. 2 and 3.

(1) is an AP line, and consists of a stainless strip continuous annealing furnace (2), a pickling device (3), a water washing device (4), a drying device (5), and other facilities.

(6) is a preheating stage installed in the front of the first section (7) of the annealing furnace (2), (9) a waste gas pipe installed in the front of the preheater (6), (10) waste gas introduced into the waste gas pipe The waste heat boiler 11 used as a heating source is a supply pipe for supplying steam from the waste heat boiler 10 to a subsequent equipment of the AP line or other equipment other than the above, and the branch pipes 11a, 11b, and ( The pickling device 3, the water washing device 4, and the drying device 5 are connected to each other by 11c).

(12) and (13) are heat exchangers provided on the branch pipes (11b) and (11c), respectively, and (14) is connected to the supply pipe (11) by the supply pipe (15) as a separate boiler.

The operation of the device having the above configuration will be described below.

The continuously running strip w is heated by a heating device 16 installed in the furnace 2.

The combustion gas generated therein is introduced into the preheating zone 6 to preheat the material w to about 300 ° C.

The waste gas which preheated the material w in the preheating table 6 is introduced into the waste heat boiler 10 in the waste gas pipe 9, where it heats the boiler 10 and produces steam.

This steam is supplied to each facility via the supply pipe 11 and the branch pipes 11a, 11b, 11c.

Here, each facility of the AP line will be described. First, the pickling device 3 removes the scale through the liquid flow of acetic acid or hydrogen fluoride because the material is oxidized in the annealing process to generate scale on the surface. It is a device for.

The pickling solution is then maintained at about 80 ° C at all times to promote reactions on the material surface.

In the water washing device 4, hot water is used to wash the pickling liquid attached to the material surface by pickling.

In the drying apparatus 5, drying is performed by heating air in order to remove moisture adhering to the material surface by washing.

In these apparatus, conventionally, the steam supplied from the boiler 14 via the supply pipe 15 is used as a heat source, and in the pickling apparatus 3, the steam pickling liquid is directly picked up through the branch pipe 11a. The pickling liquid is introduced into the furnace to heat the pickling liquid, and in the washing apparatus 4, hot water is produced by the heat exchanger 12, and in the drying apparatus 5, hot air is produced in the heat exchange chamber 13 and used. have.

In the present invention, the steam generated in the waste heat boiler 10 is supplied to the respective apparatuses through the branch pipes 11a, 11b, and 11c by the supply pipe 11 as these heat sources.

In this process, since the steam cannot be supplied from the waste heat boiler 10 at the start of operation, the waste gas sufficient to supply the steam from the boiler 14 and heat the waste heat boiler 10 to a predetermined temperature in the furnace 2. Is generated, the switching valves 17 and 18 installed in the supply pipes 11 and 15 are switched to stop the supply of steam from the boiler 14, and the steam from the waste heat boiler 10 is removed. To supply.

As is well known, when the auxiliary burner 10a is installed in the waste gas boiler 10 to preheat the waste gas entering the waste gas boiler 10 when the operation is started and the production amount is reduced, the boiler 14 and The same effect can be expected and the boiler 14 can be omitted (refer FIG. 4).

As apparent from the above description, in the present invention, the combustion gas generated in the furnace is once preheated to the material, and the waste gas after preheating is heat-exchanged to produce steam, which is then applied to a facility other than the subsequent facility of the annealing furnace or other lines. As a result, it becomes possible to use waste gas extremely effectively.

Here, how much energy is saved by the present invention will be described based on the data obtained by the embodiment of the present invention.

First, in the preheating of the material, the material w is heated to about 300 ° C. while passing through the preheating zone 6 by preheating by the combustion gas, so that the combustion amount of the first section 7 can be reduced by that amount. Do.

As a result, the length of the furnace can be determined by that minute.

For example, when the length of the furnace of the preheating zone is 10 m, the material preheating temperature is 300 ° C., and the length of the furnace of the first section 7 is 8 m, which is shorter by 4.5 m than the length of the normal furnace (12.5 m). can do.

By installing this preheating zone, the thermal efficiency of the material increases to 47% compared with the conventional 37% (an increase of about 20%).

In addition, for the use of steam, for example, when processing 40 tons of material per hour and heating the material to about 300 ° C in the preheating zone, the waste gas temperature supplied to the waste heat boiler is about 775 ° C. As a result, 3.5 tons of steam are obtained per hour.

When converted into calories, it is about 22,000,000 kcal / h.

This calorific value is about 15% of the calorie | heat amount used for 1 hour in the whole annealing furnace.

Therefore, when combined with the 20% savings obtained by heating the material by waste gas, the amount of heat which can be saved by the process of the present invention reaches up to 35%.

In addition, the gist of the present invention described above can be applied to, for example, a vertical furnace, and of course, it can be widely used in various heat treatment processes of steel.

Claims (1)

A metal strip continuous annealing furnace, a preheating stage provided at the front of the furnace, a waste gas pipe provided at the front of the preheating stage, and a waste heat boiler to which hot waste gas is supplied from the waste gas pipe, and from the waste heat boiler. Metal strips, each of which is supplied with heating fluid from the annealing furnace to a subsequent pickling device, a washing device, a drying device, and a heat exchanger respectively installed on the supply system entering the washing device and the drying device. Waste gas heat utilization system in annealing and pickling process.

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