SU1477990A1 - Control method for burning gaseous fuel - Google Patents

Abstract

The invention relates to power engineering and is intended for use in thermal installations when burning gaseous fuels. The purpose of the invention is to increase the efficiency of fuel combustion by improving the accuracy of controlling the ratio of fuel to oxidizer. The fuel and oxidizer are mixed before burning. The concentration of carbon monoxide in the combustion products and the local concentration of fuel at specific points in the mixture flow are measured. The degree of mixing of the fuel and the oxidizer is kept constant, determined by the deviations of the local values of the fuel concentration in the mixture from its average over the flow cross section. The oxidant consumption changes until carbon monoxide appears in the combustion products, then the fuel and oxidizer are mixed and the deviations of the local concentration of the fuel in the mixture are reduced from its average value until the carbon monoxide disappears in the combustion products. The resultant value of the concentration of fuel in the mixture over the cross section of the flow is measured and this value is used as the value determined with the subsequent change in the oxidant flow rate. In the case when it is not possible to bring the carbon monoxide content in the combustion products to zero by changing the degree of mixing and it reaches its limiting value, a signal is received to increase the air flow to the regulator. 1 il.

Description

one

The invention relates to a power system and is intended for use in thermal installations when burning gaseous fuels.

The purpose of the invention is to increase the efficiency of fuel combustion by improving the accuracy of adjusting the ratio of fuel to oxidizer.

The drawing shows a system diagram for implementing the method.

The system includes a gas supply pipeline 1 with a flow controller 2 and a pipeline 3 for supplying air with a flow regulator 4 connected to mixer 5 with an actuator 6. After mixer 5, an instrument 8 is installed in front of the combustion chamber 7 equipped with a burner over the cross section of the gas concentration flow, connected to the air flow regulator 4, and the device 9

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to determine the degree of mixing of gas and air, which is also connected to the air flow regulator 4 and to the actuator 6. Behind the combustion chamber 7 is an instrument 10 for determining the concentration of carbon monoxide in the flue 11, which is connected to the device 9 to determine the degree of mixing of gas with air

 Using the system, the proposed method is implemented as follows.

Pipelines 1 and 3 supply gas and air, respectively, to mixer 5, after which the average gas concentration in the gas-air mixture is measured by the instrument 8 Depending on the average gas concentration, a signal is sent to the air flow controller 4, which sets the required flow rate of air. This air flow rate is only approximate, due to the inaccuracy in the determination of even the gas-air mixture concentration averaged over the cross section. Next, the degree of gas mixing with air is measured using an instrument 9, which is based on an electrical gas analyzer circuit using a thermochemical detector as a sensitive element of the cell to determine the combustible components. The gas-air mixture is supplied to the sensing element through a 0.2 mm diameter capillary that moves discretely over the cross section of the flow path. The output signal according to the unbalance of the electric bridge is fed to the secondary devices - a potentiometer and an integrator. Estimation of the degree of mixing is defined as the sum of deviations of local concentrations of fuel at individual points along the flow cross section from the average value of the concentration of fuel.

At the same time, the concentration of carbon monoxide in combustion products is determined using instrument 10 (an optoacoustic gas analyzer is used with a secondary recorder having a channel for the output of a control signal) a control signal is generated on

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the actuator 6 of the mixer 5, in which the degree of mixing of the fuel with the oxidizing agent varies, until the signal of the presence of carbon monoxide in the combustion products becomes zero. Thus, at approximately the predetermined ratio of fuel to oxidizer, fuel combustion is achieved.

Simultaneously with the disappearance of carbon monoxide in the combustion products and the cancellation of the command to change the degree of mixing, the signal from the device 9 to the air flow controller 4 is signaled to reduce the air consumption until the appearance of carbon monoxide in the combustion products.

After the device 9 has received a signal about the presence of carbon monoxide in the combustion products, the command on the air flow controller 4 is switched off. In this case, a control signal is supplied from the device 9 to the actuator 6 for changing the degree of mixing of the fuel with the oxidizing agent in the mixer 5 until the disappearance of carbon monoxide in the combustion products.

In the case when the content of carbon monoxide in the combustion products is not brought to zero by changing the degree of displacement and it reaches its maximum value, i.e. local fuel concentrations at certain points over the flow cross section do not deviate from its average value; device 9 receives a signal to increase air flow to controller 4. This means that the excess oxidant reaches its minimum possible level for complete combustion of fuel in the proposed chamber design 7 combustion and burner. With the last operation (an increase in the excess air), the regulation process starts when, approximately, this fuel-oxidizer ratio turns out to be less than stoichiometric. I

After determining the optimum fuel-oxidant ratio and the degree of mixing of the fuel and oxidizer, the average over the flow section value of the fuel concentration is measured by the device 8 and this value is used as the TOPLIBO-oxidizer ratio specified in the subsequent adjustment after changing the burner production tag.

Claims (1)

Invention Formula e ni The method of controlling the gaseous fuel ejection process, including the supply of fuel and oxidant, mixing them before burning, measuring the average cross-sectional flow of the fuel concentration in the mixture and changing the oxidant flow rate to achieve the specified value of the average cross-sectional flow of the fuel concentration in the mixture, differing in that, in order to increase the efficiency of combustion by increasing the accuracy of controlling the fuel-oxidant ratio, the concentration of carbon monoxide in the pro 779906 is additionally measured Combustion samples and local fuel concentration at individual points of the mixture flow, maintain a constant 5 degree of fuel and oxidant mixing, determined from deviations of local values of the fuel concentration in the mixture from its average value over the flow section, change the oxidant consumption III to the appearance of carbon monoxide in the combustion products, then they increase the mixing of the fuel and the oxidizing agent and reduce the deviations of the local values of the fuel concentration in the mixture from the average of it to the disappearance of carbon monoxide in the mixture oduktah combustion, measured poluchivshees wherein the average value of the cross section of flow in the fuel concentration sme- 20 B and use this value as a predetermined change in the subsequent flow of oxidant Air, eight I ten