JPS59179716A - Operating method of heating furnace - Google Patents

Abstract

PURPOSE:To minimize the quantity of heat loss in a heating furnace for billets for rolling by taking the information on the atmosphere temp. in each zone of the heating furnace and the information of the pressure in the furnace into an electronic computer, calculating trially the blowing rate of combustion gas and the flow rate of intruding air and operating a flue damper. CONSTITUTION:The atmosphere temp. in each zone of a heating furnace 1 for billets for rolling is measured with an atmosphere thermometer 4 and the pressure in the furnace is measured with a furnace pressure gage 5, then the information on the respective actually measured values is taken into an electronic computer 8 in the stage of heating steel materials 3 to a prescribed temp. by burners 2 in the furnace 1. The blowing rate of combustion gas and the flow rate of intruding air are trial-calculated in the computer 8 and a flue damper 7 is operated to minimize the quantity of the heat loss owing to the blowing out and the intruding air by which the pressure in the furnace is controlled.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a heating furnace operating method, and proposes a heating furnace operating method that can minimize the amount of heat loss.

For example, a billet heating furnace for rolling is a heating device whose purpose is to heat a cold billet or a hot billet to a temperature necessary for rolling using coke oven gas or the like as fuel. Generally, a billet heating furnace for rolling has a plurality of openings, such as a billet charging inlet, an extraction port, and other viewing windows. In this opening, the furnace pressure is 0tanHpO at any location.
However, in reality, it will not be a 01 penalty due to buoyancy due to combustion gas, pressure distribution in the height direction of atmospheric pressure, pressure loss in the flue, etc. That is, the first
As shown in Figures (A) and (B), 9, opening AP (charging port,
The pressure distribution in the height H direction of the extraction port changes from glass (+) to minus (-) at the height of the extraction port. Therefore, if the pressure of the combustion gas in the furnace is higher than the atmospheric pressure, the combustion gas GS will blow out9, and conversely, if the atmospheric pressure is higher, air will enter the furnace AR. Note that Fa is the hearth, Fb is the inside of the furnace, and F
c is the furnace lid, AI is the blowout area, and A2 is the suction area.

Therefore, the influence of the heat consumption unit 5 is as shown in Fig. 2 (a) to (c). In other words, FIG. 5(A) shows an ideal state in which there is no blowing out of gas or intrusion of air.

In addition, the same figure (b) shows the case where gas is blown out, and the same figure (a) shows the case where there is intruding air. If there is a large amount of air, the amount of fuel increased to heat the infiltrated air will increase the amount of exhaust gas, but some of it can be recovered by the requive letter. Therefore, if the heating furnace is operated with these considerations in mind, it will be possible to operate the heating furnace in a way that minimizes the amount of heat loss.
It's difficult.

In other words, conventionally, the pressure inside the heating furnace is set and feedback control is performed based on the actual measured value of the furnace pressure. 'Furthermore, the fuel gas flow rate was generally feedback-controlled by inputting information about the furnace atmosphere temperature or billet temperature and checking the difference from the set value. Therefore, it is difficult to immediately operate a heating furnace to minimize the amount of heat loss, even in unsteady operations such as changing holes or waiting for rolling due to changes in rolling conditions.

The present FJA provides a heating furnace operating method aimed at solving such difficulties. That is, the present invention provides a heating furnace for rolling billets covered with refractories, in which atmospheric temperature information and furnace pressure/i# information for each zone of the heating furnace are input into an electronic meter, and the information is calculated by the computer. This heating furnace operating method is characterized by calculating the amount of combustion gas blown out and the amount of intruding air, and operating the flue damper so as to minimize the amount of heat loss due to the blown out and intruding air. below,
The present invention will be explained based on the embodiment shown in the drawings.

FIG. 3 is an explanatory diagram of the apparatus for carrying out the present invention. As shown in the figure, the steel heating furnace 1 includes a plurality of burners 2, an atmosphere thermometer 4, a furnace pressure gauge 5, a requiberator 6, and a flue. It is equipped with a damper 7 and the like, and heats the steel material 3. 8 is an adult cow calculator, 9 is a flow rate control device, and 10 is a gas blower 1.
11 is an air blower, and 112 is an air-fuel ratio setter. These are provided under conditions that satisfy electrical instrumentation technology and control technology.

The present invention is a heating furnace for rolling billets covered with a well-known refractory material, in which actual measurement value information from an atmosphere thermometer 4 and actual measurement value information from an in-furnace pressure gauge 5 of the heating furnace tank is transferred to an electronic computer 8. The calculator 8 calculates the amount of combustion gas blown out and the amount of incoming air, and operates the flue damper 7 to control the pressure inside the furnace so that the amount of heat lost due to the blown out and incoming air is minimized. be. As a result, the actual amount of heat loss can be grasped, and the optimum furnace pressure can be determined for the internal pressure of the heating furnace 1. Therefore, the heating furnace can be operated to minimize the amount of heat loss, and an energy saving effect can be achieved.

The above will be explained more specifically as follows.

(1) Furnace pressure: Furnace pressure is expressed by the following formula, blowing out at ΔP>0,
Suction occurs when Δp<o.

Here, Pp = Pt + P2 Pl: Atmospheric pressure (mHzo) P2: Buoyancy [11III] H: Pressure gauge mounting height (m) Tg: Furnace temperature [U] TO: Outside temperature [℃] P: Setting Pressure [mlI] (2) Calculation of blown gas amount and intruding air amount: Intruding air fit into the blown gas placement plate V Nm3. /m is determined by the following formula.

ΔPX2g u = k ( ) i ρ V: Intruding/blowing gas it (N m3/ )ir)
Tg: v person/Blowout gas temperature (℃) ΔP: Pressure difference (order & 0) Opening width (m) h: Opening height (m) U: Gas flow rate (m/a) k: Flow coefficient (-) Here, the flow coefficients are determined as shown in (,) to (f) below for the opening shapes shown in (a) to (f) in FIG.

(,) When the diameter of the opening (diameter for circular diameter, hydraulic radius for other cross sections) is more than twice the wall thickness δ, a
= 0.38 (f = 1.6) (b) When the thickness of the furnace wall is 2.5 to 3 times the opening diameter, a = 0.67 (f =
0.5). In addition, when it is 05 to 25 times (,) (b
).

(c) When the thickness of the furnace wall is three times or more the diameter, in this case,
Let f be 0.5 up to the first three times the number 1, and thereafter calculate by considering only the friction loss on the wall surface of the opening.

Therefore, a < 0.67 (d) when the gas inlet is open, A = 0.9 ~ 0.95 (f = 0.1 ~ 0
．． 05') When molten matter is attached, as in the Hayashi side of (d), a = 0.9. (f = 0.1) (e)
It takes a value between (,) and (b).

(f) Add the pressure loss of 9 angles to (b) or (c) to the gap of a general door.

(3) Heat loss due to blowing and air intrusion: Loss in unit heat quantity due to blowing Qg41. ．． ．． If the loss of unit heat due to intruding air is Qfi 4, the total Qt of both is Qt = Qg + Qa, and! By determining ΔP such that ΔP is equal to ΔP, the quantity for determining the optimum furnace pressure can be obtained.

Here, W: Blowout gas amount (Nm3/H) ΔF = Fuel increment (Nm3/H) Vex: Exhaust gas amount (Nm''/Nm3) Cpg: Gas constant pressure specific heat [-/Nm3°C] Tg: Furnace temperature [°C] Tg': Exhaust gas temperature [℃] TO: Outside temperature [℃] Ton: Processing tonnage (T/1() ηNilecu efficiency [-] Even if there is intruding air, Tg' and η are assumed to remain unchanged. .

On the other hand, the fuel increment ΔFNm3/hr due to intruding air is V
-Cpa -(Tg'-TO)+ΔF'VexCpg
'(Tg'-TO)-1-Lt-ΔFV: Amount of intruding air (Nm"/hr': JCpa: Average specific heat of air [
ICmI/Nm3℃]HL: Fuel net calorific value (Kcal/
Therefore, the actual measured values of the furnace atmosphere temperature gauge 4 and furnace pressure gauge 5 shown in FIG. 3 are taken into the electronic computer 8,
Calculations are made based on the above idea, and a control signal is output to the damper 7 to control the furnace pressure so as to minimize the amount of heat loss due to blowing and intruding air. Therefore, the results of an experiment using a pusher-type billet heating furnace having the following specifications will be explained.

Heating furnace specifications: Furnace type: Pusher type two-zone heating furnace. Dimensions・・・・・・Furnace length 2084
6,, furnace width 19825.

Furnace height (max) 2200o Effective hearth area...
・・376 m2゜Hearth load------max
357 rNormal 208 Kg/m2hr 0 burner・・・・・・・・Heating zone/soaking zone coaxial flow burner 61
9 pieces. Heating capacity: Standard 70T/H, maximum 120 pieces M0 heating material dimensions: 120 medium ×
18000° Operating conditions Furnace temperature (Tg) Atmospheric temperature (TO) -25°C Exhaust gas x in degrees (Tg'): Tg' = 4500 Pressure gauge installation height f () Opening width and opening height flow coefficient Ni: Ni=o, c+7 Specific heat Cpa, Cpg: Gas constant pressure specific heat Cpg=0.334
Kai/Nm”℃Air constant pressure specific heat Cpa=0.310
Ktal/Nm'℃ exhaust gas amount Vex: Vex =
5.6 Nm3/Nm3 Fuel net calorific value HA: H1=
4500 “ml/Nm” Recuperator efficiency η: η
= 0.3 Door opening time (per billet) 2 charging ports: 30 seconds/direction (extraction port: open) Extrusion port: 40 seconds/time The reading of the pressure gauge for pressure setting is supposed to be a stop in principle, but
Actual measurement data shows that they are equal to 11, so they are both set to have a value of 1.

As a result, as shown in Fig. 4, the set furnace pressure at which the loss of one unit of heat consumption is the minimum is 1.5 to 1.6 tanHxO. Set up and operate. The basic unit of heat loss at that time is approximately 3.18X 10
3 (s o T/1-i) ~ 2.59X10- (
12oT/H).

The damper 7 adjusts the optimum furnace pressure of 1.5 to 1.6 ttrmHs as shown in FIG. 4 according to the output from the Kameko computer 8.
It is controlled to be O. On the other hand, in the conventional method, the pressure inside the heating furnace is set and feedback control is performed using the actual measured value of the furnace pressure, and the fuel flow rate is calculated based on the difference between the set value and the fuel flow rate. Since feedback control is performed while observing the range W in Fig. 4,
There is a control ramp that results in a furnace pressure of 25 to 3.0 1 (20).Therefore, the heat loss is about 4 times worse than that of the present invention. ).

As described above, the present invention can appropriately control the furnace pressure with a precision not seen in the past, and therefore, as described above, it is advantageous in that it can operate while minimizing the amount of heat loss.

[Brief explanation of the drawing]

Figures 1 (a) and (0) are diagrams illustrating air intrusion and gas blowout at the opening of the heating furnace, and Figures 2 (a) to (0).
c) is a diagram showing the heat balance based on Fig. 1 (a) and (b), and Fig. 3 is an explanation of the present invention.
Is the figure showing the change in heat loss intensity with furnace pressure? Graph shown, 5th
The figure is an explanatory diagram of flow rate counting. In the drawing, 1: heating furnace, 2: burner, 3: steel, 4: ambient temperature #f, 5: furnace pressure gauge, 6: recuperator, 7
: damper, 8: autolift, 9: flow rate control device, lO: gas blower-y'1], : ]9-'A blower 1
12: Air-fuel ratio setting. Applicant Nippon Steel Corporation Patent Attorney Minoru Aoyagi Procedural Amendment (voluntary) May 7, 1988 1. Indication of the case Application No. 55890 dated 1988 2. Name of the invention Heating furnace operating method 3. Relationship with the case of the person making the amendment Patent applicant address: No. 3, 2-6 Otemachi, Chiyoda-ku, Tokyo Name (
665) gr Nippon Steel Corporation Representative Takeshi 1) Yutaka 4, Agent Address: 101 H [No. 5, Iwa 2IJ Tada-chome 4, Chiyoda-ku, Tokyo ← Sen Building 5, date of amendment order None 6, Number of inventions increased by amendment None 7, Comparison of amendment Column 8 for detailed explanation of the invention in the specification, Contents of amendment (x) Specification letter i 2 M4 line I"'io-"ve
rio""/, correct to +.

Claims (1)

[Claims] In a steel billet heating furnace for rolling covered with refractories, atmospheric temperature information and furnace pressure information in each zone of the heating furnace are input into an electronic computer, and the computer estimates the amount of combustion gas blown out and the amount of intruding air. A heating furnace operating method characterized by operating a flue damper so as to minimize the amount of heat lost due to blowing out and intruding air.