DD152851A1 - HUBBALING OVEN WITH TOP HEATING FOR RECYCLING LONG KNOB - Google Patents

Abstract

The invention relates to a Hubbalkenofen with Oberbeheizung for warming long Knueppel especially for use in continuous wire and fine steel rolling mills. The invention aims to ensure that the technically, economically and economically suitable for rolling mill operation suitable Hubbalkenofen with Oberbeheizung for warming long Knueppel using the full heat technically possible Herdflaechenleistung can be applied without dasz significant increase in investment costs, energy consumption, and the Kühlanbedarfs Reparaturanfaelligkeit and thus downtimes occur and without dasz operating disturbances caused by discarding and falling over of the billets due to one-sided warming, which lead to constant disturbances of the rolling operation at high power. This is achieved by partially heating the billets at the feed end of the walking beam furnace in sections by means of heating pockets and high-speed burners, so that the high one-sided temperature differences that cause the discarding do not occur at the start of the knob heating.

Description

Application of the invention

The invention relates to overhead heating beam furnaces for heating long billets of steel to rolling temperature, which are mainly used for continuous wire and stand-alone rolling mills. This type of furnace allows savings in energy, investment, maintenance and servicing costs compared to full underfloor heating furnaces Avoid unwanted chill in the feed without any additional effort, since the top-heated oven compared to the under- and superheated requires no water-cooled beam »With relatively long billets (10 to 14 m in length), however, the full, per se possible furnace performance can not be exploited the billets bend convexly as a result of rapid unilateral heating up, fall over and so constantly disturb the transport of material · To avoid this, would have for a given power several or longer ovens with the appropriate effort, energy and un d manpower needs to be built or special designs applied. This is the field of application of the invention.

Characteristic of the known technical solutions

The following walking beam furnace types and / or devices for heating long billets are known:

1 « Walking beam furnace with complete top and bottom heating

Here the billets lie on water-cooled beams and are transported by beams, which are also water-cooled, between them. · The burner is heated by burners located above and below the billets.

advantages £

High performance with short oven length, low space requirement, no discarding of long billets due to unilateral rapid heating «

High energy and cooling water consumption, high construction and repair costs j Very deep kiln cellar, cooling shadows (black spots) on the feed material above the support points, bending of the hot billet between the support points due to the dead weight, resulting in transport faults,

Walking beam furnace with partial underheating

Here, the billets are only in a part of the preheating or * heating zone on water-cooled beams and v / erden there heated from below and above, while in the remaining part of the furnace uncooled masonry fixed and movable hearth beams are used and the- heating only from above he follows.

benefits ^

Higher performance with the same kiln length compared to the only overheated kiln possible · lower energy consumption than with over- and under-fired ovens, no warping of the billets due to unilateral rapid heating, no sagging of hot billets at the discharge end of the kiln, no strong cooling shadows on the heated billet,

Additional energy consumption through water cooling in the underheated area, very low kiln wedge, relatively high construction and repair costs, additional cooling water consumption «,

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3 · Lifting beam ovens with partial underheating through pockets between pest and lifting bar

In this design, the existing of ceramic material plague and walking beam in the preheating zone (material inlet) are narrow and tapered. "The resulting pockets in the oven are heated so that the feed is partially heated from below and that far, that no obstructing operations caused by thermal stress in the billet.

Advantages:.

No energy-consuming water cooling, no discarding of the feedstock, no cooling water consumption, no appreciable shades of shadow, full exploitation of the kiln power, which is not possible with top heating, no deep basements, relatively short kiln length, low energy consumption, no bending of the hot billets.

The plague and walking beams are highly stressed mechanically and thermally and are highly susceptible to repair. Due to the slim conical design and heat application on all sides as described above. arranged pockets, the repair vulnerability is further increased, with each repair requires the shutdown of the furnace and the mill supplied by him, the downtime due to the required cooling, repair and heating time of the furnace is at least 3 to 4 days, resulting in production loss to Polge Has.

.4, S ₁ Lifting barSfeiLJlit. Upper heating;

This type of construction is well suited for relatively short billets · When used for long billets, the hearth area power must be greatly reduced to avoid discarding of the billets in order to avoid inadmissible temperature differences in the billet

Advantages ^ Y / ie under 3 ·

Extremely long preheating zones must be provided for long sticks, whereby longer or more ovens must be built for a certain performance · This requires a higher space requirement, higher investments and, in the case of several ovens, more operating personnel · Furthermore, there is no possibility of influence, if in spite of everything certain types of billets occur, except throttling performance *

5 · Stove ovens with top heating and convex stove in

the preheating zone.

This type of construction does not attempt to prevent warping, but adapts the shape of the hearth to the likely course of the warp to prevent the sticks from falling over.

benefits ^

Easy and cheap ·

ο ο ο ο ο ο ο ο j j

Geesthacht hurry ^

The hearth curvature is suitable only for one kiln output and not for the entire power range, which is why - apart from the uncertainty of the correct dimensioning of the curvature - the falling of the billets is not prevented for other services «

6 »Lifting beam furnace with top heating and edging devices

in the preheating zone

Here, the billets are transported in the preheating by sawtooth rake on pest and walking beam and thereby constantly rotated so that no one-sided heating occurs · The rakes are made of heat and scale resistant steel and are mounted on water-cooled carriers.

benefits ^

No discarding of the sticks ·

disadvantages ^

Relatively expensive effort, increased need for repair, increased energy consumption, occurrence of cooling water requirement, stride length can not be changed.

7 · Lifting beam furnace with top heating, split lifting beam system and billet transport in the preheating zone without gap

This design applies only to furnaces for heating to Ie 'and alloyed carbon steels for the purpose of rapid heating above 700 ⁰ C equipped with shared transport system in preheating and heating zone v / ground. Here, the billets are transported on the first Hubbalkensystem without gap and only after they are at a temperature

are heated, in which no warping and thus no more falling can occur when handing over to the Hubbalkensystem sporadic

benefits ^

With relatively low Aufv / and applicable, since mainly only the control must be designed according to, not the repair vulnerability of the stove increasing internals, retrofitting possible, no additional energy and cooling water needs ·

Hur applicable to walking beam ovens with split hearth.

Informations.quellen :,

Stahl und Eisen % (1976) Nr * 9 p. 443 Stahl and Eisen 97 (1977) Nr * 13 p. 627 -

Gaswärme international Bd. 20 Kr. 10 (1971) p. 343 Gaswärme international Bd ₆ 24 Nr. 10 (1975) S "407 -

DT - AS 1943330 DT - AS 2556721 DT - AS 1813605 DT - AS 1508373 DT - OS 1558020

US 3887064

223533 7

Aim of the invention ; ,

The method and apparatus according to the invention is intended to cause long billets in a technically-economically good for rolling mill operation especially of continuous and Peinstahlstraßen suitable Hubbalkenofen with top heating without transport disturbances due to billet warping under full utilization of thermally possible max. Herd surface power can be heated, the investment cost is lower than other solutions and without the stove durability and reliability are compromised.

Explanation of the nature of the invention

The invention solves the technical problem of preventing the warping and overturning of stock billets in superheated walking beam furnace with full utilization of the possible hearth area power, in which the temperature difference between the upper and lower sides of the billet is interrupted in sections by a simple partial underheating of the inlet part of the preheating zone less than 150 K is limited, as long as the feedstock is still relatively cold and tends to warp, whereby the reliability of the original type of furnace in the inlet part is fully maintained ·

Features of the invention

The billets are conveyed, as usual, at the feed end of the furnace laterally by roller table or front side by means of lifting bar or insertion device in the oven chamber ·

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The Hubbalkenabstände are designed so that the finished heated billet no sagging during lifting and transporting occurs. In the preheating zone, the billets have a low temperature and relatively high strength, so that you can double the Hubbalkenabstand by each 2 * lifting beam (a total of an odd Hubbalkenanzahl must be provided) is so far shortened that in the resulting spaces undercutting the required may be placed _e length hereby is achieved that the lifting beam and fixed beams not weakened, but be obtained in full width and stability, since the sub-burner bags are obtained by omitting depending ?? Eils a walking beam ".

As a result, the billets are heated in the area of the pockets and not over almost the entire length from below, the heat transfer conditions are improved so that the partial under-heating in the possible heating time is sufficient to prevent warping and falling of the billets * This is by application * High-speed burners for pocket heating * The burners, which operate at the exit velocities of the partially combusted gas-air mixture from the burner block from 50 to 150 m / s, generate a strong turbulence and circulation of the flue gases in the pockets and in the area above it Since the heat transfer in this temperature range is predominantly by convection and this is greatly increased by higher gas velocity and turbulence on Wärmgut (at z, B "triple the speed doubles the heat transfer coefficient), the use of high-speed burners se one hr effective method to achieve maximum heat flow with the lowest possible temperature differences. Thus, an essential prerequisite is created to perform the heating of the billets undersides at the end of feed without energetically undesirable increase in exhaust gas temperature «

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To realize this heating method, the practical application of which is apparent from the exemplary embodiment, several devices are required ·

1 · An odd number of stroke bars must be provided ·

2 · The length of the billets must not fluctuate more than ± 0.5 m for an oven ·

3 · Each 2 lifting bars are shortened by the length of the heating bag on the charging side ·

4 · The heating bag is also used as a tundish funnel to remove the scale that falls off when the furnace is loaded · For this purpose, the bottom is formed with funnel slopes and a closable opening ·

5 · High-speed burner star is installed on the front of each heating bag · Each system consists of:

- High speed burner with burner stone

- Gas and air solenoid valves

-Verantwortregler to keep the gas-air ratio constant

- electrical ignition and flame monitoring device

- Gas and air supply line with shut-off valves

- Temperature controller or manual control in the MSR system of the furnace for remote control of the burner

embodiment

Reference to an embodiment of the invention will be explained in more detail below.

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In the accompanying drawings show:

1 is a longitudinal section through the feed end of a Hubbalkenofens with ceiling heating (upper heating) and heating pocket (Teilunterbeheizung)

Pig © 2 the cut and Pig · 1

Funnel-shaped heating pockets 3 are arranged in the feed end 1 of the lifting beam furnace according to Pig, heated from above by overhead radiation burners 2, and

The billets 4 are laterally fed through a feed opening 5 via individually driven roller table rollers 6 into the oven chamber, positioned by push-off means 7 and transported by lifting bars 8 in the direction of the discharge end 9 of the oven. The sticks are heated from above by radiant ceiling burners 2 and withdrawing flue gases. The heating pockets 3 are heated by high-speed burners 11, so that the overlying billets 4 are also heated from below on the sections located above the heating pockets 3, an intensive flue gas movement in the billet area being produced by the high-speed burners 11, since the flue gas leaving at high velocity is generated. Preistrrahl 12 a large amount of flue gas sucked in (recirculation) and is effective through the entire length of the heating bag 3 ·

When descending the billet 4 sloping scale accumulates in the funnel of the heating bag 3 and can be withdrawn periodically through the opening 13 ·

223533

The transport of the billets 4 (only two billets 4 have been shown in FIG. 2) takes place in which the lifting bars 8 move in the direction of roller table rollers 6, are raised above the upper edge of the hob, and the billets 4 from the roller table rollers 6 or the plague bar 14 lift off, move to step length to the discharge end 9, by lowering the stick 4 on the Pestbalken 14 and continue to be lowered so far that the Hubbalkenoberkante below. the plague bar surface lies ·

The high-speed burners 11 are connected to a gas distribution line 15 and an air distribution line 16 and are controlled via an air solenoid valve 18 and a gas solenoid valve 17 and a ratio-built in the gas line ratio controller 19 which is connected via a pulse line to the air terminal of the burner,

For the ignition and flame monitoring, an ignition coil and an automatic burner control unit near the burner are mounted on the furnace. The temperature is regulated in the heating pockets 3 by a temperature controller in the BMSR system of the furnace. In this example, two high-speed burners 11 per heating pocket 3 are arranged depending on the temperature deviation from the target temperature, which is detected by a thermocouple 20 are controlled by the temperature controller via the automatic burner control so that either both high-speed burners 11 are off or burn one or two high-speed burners with full load »So it is an open-To Regulation, which, in contrast to a stepless control, allows full utilization of the square of the speed increasing impulse of the burner jet.

Claims (3)

invention claims 1 «Hubbalkenofen with Oberbeheizung for heating long billets, characterized in that at the feed end (1) in the stove" lifting bar (8) and Pestbalken (14) whose supporting body is made of refractory material, heating pockets (3) are inserted, including everyone second lifting bar (8) is shortened and on the front side of the heating pockets (3) one or more high-speed burners (11) with the associated control (15 to 20) are arranged * 2 "walking beam furnace according Pkt * 1 _e , characterized in that the heating pockets (3) are formed simultaneously as Zundertrichter with a corresponding opening (13) β 3 »walking beam furnace according to point 1 · and 2«, characterized in that the plague bars (14) are simultaneously formed as side walls of the heating pockets (3). For this, .. ^ ..... pages drawings