SU514157A1 - Method of controlling the combustion process - Google Patents

Description

one

The invention relates to boiler technology and can be used to quickly adjust the combustion mode in the combustion chambers of boiler units.

Determination of losses with mechanical and chemical underburning during operation is carried out by means of laboratory chemical analysis of several fly ash and flue gas averages for several hours, which practically excludes the possibility of promptly taking measures to reduce these losses.

Regulation of the combustion mode by a known method reduces to maintaining the excess air specified by the regime map in combustion products. However, under operating conditions, where random variations in regime factors that affect the completeness of fuel combustion occur, this method of maintaining the combustion mode is not effective enough. Thus, for example, with an increase for some reason, the shortage of fuel, the concentration of free oxygen (Og) in the flue gases increases. The combustion controller, acting by a known method and maintaining the specified excess air (Og content), reduces air consumption, which leads to a further increase in losses with underburning.

The proposed method makes it possible to increase the efficiency of control over the combustion mode and reduce underburning. This is achieved by determining the amplitude or range of fluctuations of the oxygen concentration in the combustion products.

At a constant air flow rate, the amplitude of oscillations of the current excess air relative to the burned part of the fuel is determined by the magnitude of the amplitude of fuel consumption fluctuations and the magnitude of losses with mechanical and chemical underburning.

dz, l + a

oh,

where Qa + i is the average integral sum of losses with mechanical and chemical underburning for the control period;

0maxQMHH

 „MiiKC min22

2 (21 -)

- average for the same period, the relative amplitude of oscillations of an excess of free oxygen;

L - average for the same period, the amplitude of the fluctuations of the reacted fuel consumption.

Claims (1)

Since the left part of the above ratio is the sum of underburning and the amplitude of the pulsations of the reacted fuel consumption, the decrease in the ba reflects both the reduction of losses with the underburning and the decrease in the fuel supply instability. In both cases, with a decrease in 5a, the reliability and efficiency of the combustion chamber operation increases, which indicates the expediency of using the amplitude (or range) of oscillations of excess free oxygen as a criterion of the quality of the combustion process. The drawing shows one of the possible control schemes for the combustion process by the described method using an 8a or impulse (amax - "min). From sensor 1 of the free oxygen content in the final combustion products of the combustion chamber 2 of the boiler, a signal is supplied to converter 3, which determines the magnitude of the amplitude or range of oscillations of the concentration OO for a specified time using the ratio 2 (21 -). The signal from the converter is fed to controller 4 of the combustion process and alarm 5. The control system may be built as a search engine. For a given period of time, the relative amplitude of the pulsations ba is determined. If in the next cycle of determining its value increases, the controller 4 sends to the executive body 6 a command to increase the air flow by one step. The incremental increase in air flow continues until the ba is stabilized at the minimum value or starts to increase. In the first case, the search is terminated. In the second case, the search is directed in the opposite direction until the minimum value of ba or the specified minimum excess air is reached. The impulse according to the value of ba can be used in a similar way to other regime factors: air distribution between the burners, the amount of secondary air twist (for turbulent burners), the angle of inclination of the burners (for rotary burners), etc. In those cases when The amplitudes of the pulsations 02 consist in the factors that the regulator cannot influence, but the maintenance staff can take measures to increase the ba to eliminate this cause. Thus, the proposed method makes it possible to increase the efficiency of control of the combustion process due to the operative adjustment of the regime towards its optimization — by maintaining the value of ba at the minimum level. According to experimental data, a decrease in ba by 1% leads to an increase in the efficiency. boiler units are also on 1 abs. % Furthermore, the method improves the reliability of operation of the heating surfaces of the boiler units due to a decrease in the amplitudes of heat generation pulsations in the combustion chamber and gas temperatures in the heating surfaces. Claims The method of controlling the combustion process by measuring the criteria of combustion quality and influencing the fuel-air ratio, is characterized in that, in order to reduce underburning, the amplitude of the pulsations of oxygen concentration in the combustion products is used as a criterion.