JPS5914526B2 - How to operate a batch heat treatment furnace - Google Patents

Description

Detailed Description of the Invention The present invention heats a batch-type heat treatment furnace in a steelworks while quickly controlling the pressure of fuel gas (hereinafter referred to as gas pressure) to be supplied to the furnace, thereby reducing the fuel consumption rate. Regarding how to reduce it as much as possible.

Conventionally, the fuel gas to be supplied to the above-mentioned batch heat treatment furnace has a constant flame temperature, which is known empirically to reach almost its maximum during the heating period from the start of heating until the temperature inside the furnace reaches the target temperature. The fuel gas set at the gas pressure is mixed with air supplied at a constant flow rate and pressure to raise the temperature. ON-OFF control was performed to maintain the internal temperature at the target temperature.

However, the gas pressure at which the flame temperature reaches its maximum cannot be uniquely determined, but it changes from moment to moment according to fluctuations such as the state of the fuel gas supply source and the combustion state, so it cannot be determined empirically. Heating and soaking, assuming that the flame temperature can be maximum at constant air pressure and constant gas pressure known in It had many drawbacks, such as being difficult to shorten.

The present invention has been made in view of the above, and its purpose is to provide fuel gas and air (in other words, During the period of heating up to the target temperature using the empirically optimized air-fuel ratio, the fuel gas pressure is changed to maximize the flame temperature in response to fluctuations in the combustion gas supply source and combustion conditions, and the flame temperature is maintained at its maximum. The purpose is to maintain the optimum gas pressure even during the hot season, and an embodiment thereof will be described in detail below based on the attached drawings.

First, in carrying out the method of the present invention, as shown in FIG. 1, a batch heat treatment furnace 1 includes on-off valves 5, 5, A gas pressure setting device 9 is installed to control a pressure control valve 7 interposed in the fuel gas supply pipe 4.

Further, a thermometer 10 for measuring flame temperature is installed inside the batch type heat treatment furnace 1.

In this state, the gas pressure regulating valve 7 is operated by the output signal from the gas pressure setting device 9 to set the gas pressure to maximize the flame temperature during heating, and to set the gas pressure to minimize the fuel flow rate during soaking. This allows the gas pressure to be changed and set as the process progresses.

That is, during the heating period, as shown in the same figure and Figure 2A, the flame temperature of the heat treatment furnace heated by combustion of fuel gas at gas pressure P is measured with thermometer 10, and the elapsed time t just before time 81:00 is measured. From the relationship with the measured temperature value T, the following (constant K of formula D) is determined.

, K1, K2, α1, and α2, the estimated future temperature T1 at time 82:00 is determined from the virtual curve obtained using the 0 formula, and the gas pressure at 81:00 is △P>0 (P+△P). If the setting is changed to 82:00, the flame temperature will be measured.

Then, compare the future estimated temperature T1 at the time 82 o'clock obtained here with the actual measured temperature T2, and if T1 is less than T2, the following condition (■) with constant C=C1 and the minimum gas pressure change amount A is A<0 Set the gas pressure change amount △P to raise the gas pressure using the following formula (■) under the following conditions, and conversely, if T1>T2, set the minimum gas pressure change under the following condition (■) with constant C = 02. Under the condition that the amount AfJ'-A<O, the gas pressure change amount .DELTA.P is set to lower the gas pressure using the same equation as above.

Note that the conditions for ■ and ■ are based on the theoretical gas pressure P, on the assumption that the optimal gas pressure exists near the theoretical gas pressure.

If the previous gas pressure was set further away, it will be roughly manipulated to reach the theoretical gas pressure P.

and the theoretical gas pressure P.

If the previous gas pressure was set close to This is to determine the pressure change amount ΔP.

Also, during the soaking period, the gas pressure P and combustion time S at that point are
Based on ON, the average waste flow rate G during one cycle consisting of one pair of ON time and OFF time in the on-off valve 6 is calculated using the following equation 0 as shown in Figure 2.

Then, compare the previous gas flow rate G1 obtained in this way with the current gas flow rate G2, and if G1>G2, the above-mentioned constant C-C1 condition (■) and the minimum gas pressure change amount A is A>O.
Set the gas pressure change amount △P to raise the gas pressure using formula 0 under the conditions of
In order to lower the gas pressure under the condition that IJ''-A<0, the gas pressure change amount ΔP is set using the 0 formula.

The gas pressure change amount ΔP obtained in this way is output from the gas pressure setting device 9, and operates the gas pressure regulating valve 7 to maintain the gas pressure at the minimum fuel gas amount and at the same target temperature. .

(In the heating period, the method of the present invention changes and sets the gas pressure based on the change in flame temperature due to changes in gas pressure over time, and maintains the flame temperature at its maximum during the soaking period.) The gas pressure is changed and set based on the change in gas flow rate due to the change in gas pressure over the cycle time, and the previous gas pressure is located far away from the theoretical gas pressure in order to maintain the target temperature value and keep the fuel gas flow rate to the minimum. The gas pressure is rough, and the previous gas pressure located nearby is finely controlled so that it can quickly approximate the theoretical gas pressure, so it can quickly respond to fluctuations in the fuel gas supply source state and combustion state that change from moment to moment. As a result, as a result of implementing the method of the present invention in a bell type single annealing furnace, the fuel consumption rate was reduced by 15 parts, and the 02 parts in the exhaust gas at that time were reduced by 15 parts compared to the conventional one. We were able to control it from the 5th section to 2%.

[Brief explanation of drawings]

The drawings show one embodiment of the method of the present invention, and Fig. 1 is a flowchart thereof, Fig. 2A is a graph showing the relationship between elapsed time and furnace temperature during the heating period, and the opening in the figure shows the soaking temperature. FIG. G is a batch type heat treatment furnace, 2 is a combustion burner, 3 is an air supply pipe, 4 is a fuel gas supply pipe, 5 and 6 are on-off valves, 7 is a gas pressure control valve, 8 is a temperature controller, and 9 is a gas pressure setting 10 is a thermometer.

Claims (1)

[Claims] 1. Operation of a batch heat treatment furnace characterized by constantly changing and setting the fuel gas pressure so that the flame temperature is maximized during the heating period and the fuel gas flow rate is minimized during the soaking period. Method. 2 When changing the fuel gas pressure, change the setting coarsely when the previously set fuel gas pressure is located far from the gas pressure corresponding to the stoichiometric air-fuel ratio determined according to the combustion device, and finely when it is located close to it. A method for operating a batch heat treatment furnace according to claim 1, characterized in that: