JPS62164824A - Method for controlling heat pattern of continuous heating furnace - Google Patents

Abstract

PURPOSE:To minimize the amt. of the fuel to be thrown to a continuous heating furnace by igniting a preheating zone only when the presumed temp. calculated from the charging time, residence time, etc., of a slab is low in comparison with the required min. temp. of the slab on the outlet side of the preheating zone. CONSTITUTION:The slab is passed through the continuous heating furnace having the preheating zone, heating zone and holding zone and is thereby heated. The temp. in the furnace is controlled by igniting and extinguishing the above-mentioned preheating zone according to the operating condition. The required min. temp. and presumed temp. of the slab on the outlet side of the preheating zinc in the method for controlling the heat pattern of the above-mentioned continuous heating furnace are calculated and compared by analyzing the same with a process computer 20 from the respective zone temps. when the heating zone and holding zone are heated up to the limit of the heating power by igniting the preheating zone of the heating furnace, the target extraction temp. and furnace charging temp. of the slab to be charged, and the residence time of the slab in the respective heating zones. As a result, the above-mentioned preheating zone is automatically ignited by controlling a flow rate control valve 23 and flow rate value 24 for fuel and a flow rate control valve 21 and flow rate valve 22 for air for combustion when the presumed temp. is lower than the required temp. mentioned above.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a heat pattern control method for a continuous heating furnace.

[Conventional technology]

Continuous slab heating furnaces typically have multiple combustion zones.

The most common type is a six-zone heating furnace, which consists of an upper and lower pre-heating zone, an upper and lower heating zone (1), and an upper and lower soaking zone (1). Each of these zones has different operating methods depending on its purpose. Among these, the preheating zone is the operating mode (load condition)
, the heat pattern is adjusted by igniting and extinguishing according to the slab characteristics (thickness), aiming to reduce the fuel consumption rate.

[Problem that the invention seeks to solve]

As mentioned above, in continuous heating furnaces, the fuel consumption rate is reduced by igniting and extinguishing the preheating furnace depending on the operating mode and slab characteristics, but the timing of ignition and extinguishing is based on the experience of the reactor operator. As a result, the amount of fuel input differs depending on the individual, resulting in wasted fuel usage.

The present invention solves the above problems and provides a heat pattern control method for a continuous heating furnace that minimizes the amount of fuel input.

[Means for solving problems]

The present invention aims to solve the problems of the prior art described above, and employs the following method.

When the pre-heating zone of the continuous heating furnace is extinguished and the heating zone and soaking zone are heated to the heating capacity limit, what is the temperature of each of the heating furnaces? i; temperature and
From the extraction target temperature of the slab to be charged and the temperature at the time of charging into the furnace, and the residence time of the slab in each heating zone, calculate and compare the required minimum temperature of the slab at the outlet side of the pre-preparation zone with the expected temperature, and calculate the required temperature. This is a method in which the preheating zone is ignited only when the expected temperature is lower.

[Effect]

It is necessary to ignite the operating core tropics when the extraction target temperature required for the slab cannot be obtained within the specified furnace time even if the heating zone and uniform zone are heated to the heating running power limit. .

In the present invention, a heat transfer equation consisting of known quantities of each temperature of the heating furnace, the extraction target temperature of the slab, the furnace charging temperature of the slab, and the residence time of the slab in each heating zone is analyzed by computer, The required minimum temperature and expected temperature of the slab at the exit side of the preheating zone are calculated in advance.

Therefore, unlike the conventional method, the preheating zone is automatically ignited when the required temperature of the slab is higher than the expected temperature, without relying on the experience of the reactor operator.

〔Example〕

The method of the present invention will be explained below.

The following amounts are known depending on the temperature characteristics of each zone of the heating furnace, the slab extraction pinch, and the extraction target.

TO Extraction target temperature of varnish slab, tOS Residence time in the parallel part of the varnish slab furnace tp Residence time of the varnish slab in the preheating zone th Residence time of the varnish slab in the heating zone LS Residence time in the soaking zone of the varnish slab 12 0 Residence time in the varnish slab furnace Charging temperature Ohmax: Furnace temperature when the heating zone is heated to its heating capacity limit Osmax: Evenly distributed; Furnace temperature when heated to the heating capacity limit 11 Jpmin: Preheating at pre-8-1'f extinguishing; 2 Furnace temperature Oo min: Initially from the operating condition of the furnace butt parallel part temperature at the time of pre-heating zone extinguishing. Preheat the slab a; 2. Find the required minimum temperature Th on the outlet side.

The required minimum temperature Th is the slab extraction target temperature TO1 heating zone, uniform/8 zone teno residence time th, ts, furnace temperature Ohmax when heating zone, uniform 8 zone is heated to the heating capacity limit,
It can be obtained by solving the heat transfer equation consisting of Osmax. This calculation is done using Figure 1, but
In FIG. 1, the horizontal axis shows the time in the furnace, and the vertical axis shows the temperature.

Next, the assumed temperature Tm at the exit side of the preheating zone when the slab passes through the preheating zone with the preheating zone extinguished is determined.

The assumed temperature Tm is the temperature at the time of furnace charging, 0. It can be determined using a heat transfer equation consisting of residence times tp and th in the parallel part of the furnace tail and the preheating part, and temperatures Opmin and Oomin of the parallel part of the furnace tail and the parallel part at the time of extinguishing the preheating zone.

Therefore, When T h > T m, the preheating zone is ignited.

When Th≦Tm, the pre-heating zone is extinguished.

do it.

In addition, considering the error in residence time, T h > T m + α ignite the preheating zone, Th≦Tm
+α Extinguish the preparatory zone.

(α is the correction value) Next, the method of the present invention will be explained with reference to the flowchart shown in FIG.

■ Heating furnace 6-zone temperature characteristics Ohmax, Osmax
, Opmin, Oomin, number of slabs to be processed N,
Set the initial value of counter i=o.

■ Counter, ■ Determining whether or not all slabs have been processed, ■ Inputting data such as slab-specific data, To, to, tp, th, ts, and temperature 0 when charging the furnace, ■ Exiting the slab from the preheating zone. Calculation of the required minimum temperature Th on the side.

■ Calculation of the assumed temperature Tm at the exit side of the slab preheating zone, ■ Comparative judgment, (b) Ignition of the preheating zone, ■　Extinguishing of the preparatory zone, aΦ Heating of the slab, This completes one series of heat treatments (return to step 3).

FIG. 3 shows a diagram of a heating control system for carrying out the method of the present invention, in which a process computer 20 is used as a computer.

The heating control system is composed of process calculation a 20° temperature sensors, I& volume valves 22, 24, flow rate controllers 21, 23, automatic ignition/extinguishing controller 25, etc.

After setting the initial values in the flowchart (1) shown in FIG. 2, the process computer 20 executes calculations and judgments in each step of the flowchart (2) to (2), and based on the results, the process computer 20 executes the calculations and judgments in each step of the flowchart (Q).

By executing steps 6+ and 11'o), the air and fuel flow rate controller 21.23 is controlled to open and close the air and fuel flow:l''L valve 22.24, and the point extinguishing point 1
] The dynamic controller 25 is controlled to turn on and extinguish the burners in the preheating zone.

In this way, the required minimum temperature at the exit side of the preheating zone of the slab can be ensured with the minimum energy input jd.

〔Effect of the invention〕

According to the method of the present invention, based on the operating conditions and slab characteristics, the required minimum temperature on the outlet side of the heat sink and the assumed temperature are calculated by a computer, and as a result, by comparing the two, the ignition of preheating step 12,
Since it is possible to extinguish the fire and control the heat pattern of the heating furnace, it is effective in reducing the amount of fuel used compared to the conventional method based on the experience of the furnace operator.

[Brief explanation of drawings]

Figure 1 is an example of a graph used to calculate the required minimum temperature of the slab at the exit side of the preheating zone according to the method of the present invention.
FIG. 2 is a flowchart of the method of the present invention, and FIG. 3 is a diagram of a heating control system for carrying out the method of the present invention shown in FIG. 20... Process computer 21.23... Flow hi controller 22.24... Flow rate valve 25... Point extinguishing automatic controller TO = Slab extraction 11 standard temperature, tO At the bottom parallel part of the varnish slab Residence time tP Residence time of the varnish slab in the preheating zone th Residence time of the varnish slab in the heating zone tS Residence time of the varnish slab in the soaking zone 0 Temperature when charging the varnish slab into the furnace Ohmax: The heating zone was heated to the heating capacity limit Furnace temperature at the time Osmax: Furnace temperature when the soaking zone is heated to the heating capacity limit θpmin: p Preheating zone furnace temperature at the time of tropical fire extinguishing Oomi
n: Temperature of the parallel part of the furnace tail when extinguishing the preheating zone Th: Required minimum temperature of the varnish slab at the exit side of the preheating zone Tm Estimated temperature N of the varnish slab at the exit side of the preheating zone Number of varnish slabs i: Counter α; Supplementary I [value

Claims (1)

[Scope of Claims] 1. A heat pattern control method for a continuous heating furnace in which the temperature inside the furnace is adjusted by igniting and extinguishing a preheating zone depending on the operating state, wherein the heating zone and soaking zone are controlled by extinguishing the preheating zone of the heating furnace. From the temperature of each zone of the heating furnace when heated to the heating capacity limit, the extraction target temperature of the slab to be charged, the temperature at the time of charging the furnace, and the residence time of the slab in each heating zone, the exit side of the pre-heating zone is determined. A heat pattern control method for a continuous heating furnace, comprising: calculating and comparing the required minimum temperature of the slab with an expected temperature, and igniting the preheating zone only when the expected temperature is lower than the required temperature.