JPS62158905A - Method of recirculation and changing-over in combustion of discharging gas in coke oven - Google Patents

Abstract

PURPOSE:To improve safety when a combustion chamber is changed-over while combustion operation is carried out by a method wherein a fuel gas supplying starting time precedes by a proper amount of time a supplying starting time of a discharged gas recirculation system. CONSTITUTION:When a change-over signal for a combustion chamber is generated, a shielding signal is generated from a control part 14 to shielding operation parts 15 and 15' to fully close a discharged gas flow rate adjusting valve 7 and a fuel gas flow rate adjusting valve 9 so as to change over combustion chamber changing-over valves 16 and 16'. Then, the shielding signal is cancelled to open the valves 7 and 9, and when supplying of gas is restarted, the valves 7 and 9 are controlled in such a way as the supplying of fuel gas precedes by a proper time that of discharged gas. This controlling operation is performed such that a supplying starting time of the fuel gas adjusting valve 9 proceeds by a time of DELTAT that of the discharged gas adjusting valve 7.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust gas recirculation switching combustion method in a coke oven.

(Prior art and its problems) As a measure to reduce NOx in coke ovens, exhaust gas recirculation involves supplying combustion gas, which is a mixture of part of the exhaust gas from the combustion chamber with fuel gas, to the combustion chamber and combusting it. Combustion method is used. At this time, the fuel gas and exhaust gas are mixed by controlling the flow control valves of each system so as not to create an explosive atmosphere and to maintain a predetermined amount of heat. However, coke ovens have a structure in which combustion is performed by switching between a pair of combustion chambers, and after stopping combustion in one combustion chamber, when supplying combustion gas to the other combustion chamber, the It is very difficult to achieve a predetermined mixing ratio since it is difficult for the flow rate control valve to function properly at the beginning of the process. However, the oxygen concentration in exhaust gas is about 10%, and only coke oven gas (for example, coke oven gas) can be used as a fuel gas.
Since COG) also contains about 18% oxygen,
Depending on the mixing ratio, there is a risk of creating an explosive atmosphere and causing the mixture to evaporate.

The present invention solves the above-mentioned conventional problems and eliminates explosive atmosphere when switching between paired combustion chambers for combustion when exhaust gas recirculation combustion is performed as a measure to reduce NOx in a coke oven. The purpose is to ensure safety by preventing such occurrences.

(Structure and operation of the invention) That is, in order to achieve the above-mentioned object, the present invention provides a pair of combustion chambers that are switched to perform combustion, and a part of the exhaust gas from the combustion chambers is mixed and combusted. In a configuration in which gas is supplied to the combustion chamber as a fuel gas, when switching combustion, the supply of the fuel gas system and the exhaust gas recirculation system is stopped to stop combustion in one side of the combustion chamber, and then the other side is stopped. When supplying combustion gas to the side combustion chamber, the valve devices of each of the systems are controlled so that the fuel gas supply start time precedes the exhaust gas recirculation system supply start time by an appropriate amount of time. That is. A detailed description will be given below based on drawings showing examples of specific configurations.

Reference numeral 1 indicates a coke oven, and the coke oven 1 is provided with a pair of combustion chambers A and B and a carbonization chamber C.
, B are switched and burned. Reference numeral 2 indicates a mixer, and 3 indicates a combustion gas system extending from the mixer 2 to the combustion chambers A and H. Further, reference numeral 4 indicates an exhaust gas recirculation system from the combustion chambers A and B to the mixer 2,
Reference numeral 5 indicates a discharge pressure regulating valve of the blower 16, and reference numeral 7 indicates an exhaust gas flow regulating valve.

Next, reference numeral 8 indicates a fuel gas system leading to the mixer 2, and reference numeral 9 indicates a fuel gas flow rate control valve.

In the above configuration, the fuel gas that has passed through the fuel gas system 8 and the exhaust gas that has passed through the exhaust gas recirculation system 4 are mixed in the mixer 2, and are passed through the combustion gas system 3 as combustion gas.
It is supplied to either side of the combustion chambers A or H and is used for combustion. The calorific value of the combustion gas is calculated based on the calorific value of the fuel gas and the flow rate signal from the calorimeter 11 and the flow meter 12, for example, according to the calorific value set in the calorific value setting unit 10, and the mixed amount of exhaust gas is calculated. Based on this, a control signal is given to the flowmeter 13 to control the exhaust gas flow rate control valve 7, thereby making it possible to maintain the flow rate at a predetermined value.

When switching combustion, when a combustion chamber switching signal is issued, the control section 14 first issues a shutoff signal to the shutoff operation section 15, 15, fully closes the exhaust gas flow rate control valve 7 and the fuel gas flow rate control valve 9, and then Switch the combustion chamber switching valve 16.16. Thereafter, the shutoff signal is released, the exhaust gas flow rate control valve 7 and the fuel gas flow rate control valve 9 are opened, and the supply of combustion gas to the switched combustion chamber is resumed. As described above, the exhaust gas flow rate control valve 7 and the fuel gas flow rate control valve 9 are controlled so that the time point at which fuel gas supply is started is an appropriate amount of time earlier than the time point at which exhaust gas supply is started. The outline of this control operation is as shown in the time chart of FIG. 2, in which the supply start time of the fuel gas flow rate control valve 9 is made to precede that of the exhaust gas flow rate control valve 7 by 47 hours.

When controlled in this way, when the exhaust gas flow rate control valve 7 is opened and exhaust gas is supplied to the mixer 2, fuel gas has already been supplied, so the time when the exhaust gas flow rate control valve 7 is fully opened Even if the operation is unstable and more than a predetermined amount of exhaust gas is supplied, the combustion gas will not become an explosive atmosphere.

The time ΔT can be set as appropriate depending on the flow rate of each system 4.8, and the opening degree can be gradually increased after opening the respective flow rate control valves 7 and 9 until the steady state is reached. It is also appropriate to control the amount. In the figure, reference numeral 17 is an oxygen concentration analyzer, and the control section 14 may be additionally controlled based on the oxygen concentration measured by this analyzer 17.

(Effects of the Invention) As described above, the present invention provides a coke oven in which a pair of combustion chambers are switched to perform exhaust gas recirculation combustion. When stopping the supply of fuel gas to stop combustion in one side of the combustion chamber, and then supplying combustion gas to the other side of the combustion chamber, the fuel gas supply start point is set to be lower than the exhaust gas supply start point. Since the valve devices of each system, that is, the flow control valves, are controlled in advance by an appropriate time, even if the flow rate adjustment is unstable at the time when these flow control valves start supplying fuel, the fuel Gas is supplied in advance, so
It has the special effect of being able to always maintain the combustion gas outside the explosion range, that is, above the upper explosion limit, and thus effectively ensuring safety when switching between the paired combustion chambers for combustion. .

[Brief explanation of drawings]

FIG. 1 is a system explanatory diagram showing an embodiment of an exhaust gas recirculation switching combustion system of a coke oven to which the present invention is applied, and FIG. 2 is a time chart showing an example of the operation of the present invention. Code 1: Coke oven, 2: Mixer, 3: Combustion gas system, 4: Exhaust gas recirculation system, 5: Prower 16: Discharge pressure regulating valve, 7: Exhaust gas flow rate control valve, 8... Combustion gas system, 9... Fuel gas flow rate control valve, 10... Calorific value setting section, 11... Calorimeter, 12.1
3...Flowmeter, 14...Control unit, 15, 15'...
・Shutoff operation part, 16° 16'... Combustion chamber switching valve, 17
...Oxygen concentration analyzer, A. B... Combustion chamber, C. Carbonization chamber.

Claims (1)

[Claims] In a configuration in which a pair of combustion chambers that are switched to perform combustion are provided, and combustion gas that is a mixture of fuel gas and part of the exhaust gas from the combustion chambers is supplied to the combustion chambers, when the combustion is switched, the fuel gas system Then, when supplying the exhaust gas recirculation system is stopped to stop combustion in one side of the combustion chamber, and then when supplying combustion gas to the other side of the combustion chamber, the fuel gas supply start point is set at the exhaust gas level. An exhaust gas recirculation switching combustion method in a coke oven, characterized in that the valve devices of each of the systems are controlled so as to precede the supply start point by an appropriate amount of time.