Operation evaluation method for additional inlet air of tangential firing tilting nozzles

Abstract

The invention discloses an operation evaluation method for additional inlet air of tangential firing tilting nozzles. The operation evaluation method comprises the steps that a total secondary air flow entering a hearth is obtained according to the total air inlet amount and the total primary air flow of the hearth; primary air density and secondary air density are separately calculated, and the average density of primary air and secondary air and the average speed of primary air nozzles and secondary air nozzles are obtained; the air speed of each secondary air nozzle and the total amount of air entering the hearth through the secondary air nozzles are calculated; and the additional inlet air amount of the tangential firing tilting nozzles is obtained by subtracting the total amount of the air entering the hearth through the secondary air nozzles from the total secondary air flow entering the hearth, and the ratio of the total secondary air flow entering the hearth to the total amount of the air entering the hearth through the secondary air nozzles serves as a nozzle additional inlet air coefficient. The operation evaluation method has the beneficial effects that the nozzle additional inlet air amount is evaluated by utilizing secondary air resistance characteristics and a hearth resistance coefficient which are measured at a cold state; and an evaluation result is used for diagnosing the operation state of the combustor nozzles.

Description

technical field [0001] The invention belongs to the field of operation monitoring and diagnosis of a pulverized coal burner of a boiler, and in particular relates to an operation evaluation method for additional air intake of a tangential combustion swing nozzle. Background technique [0002] It is an effective means of combustion design, control and optimization to send in the right amount of air at different stages of pulverized coal combustion. Therefore, tangential coal-fired boilers are equipped with air and fuel nozzles with different functions at different heights of the furnace, usually including primary air, Auxiliary secondary air, peripheral air, compact overburning air, separated overburning air, and the "fire downwind" at the bottom, etc., through the organized air distribution of these nozzles, the furnace maintains a reasonable distribution of air powder to improve the coal powder Burnout degree, reduce the formation of nitrogen oxides, and meet the needs of s...

AI Technical Summary

Problems solved by technology

[0003] Compared with the air distribution of organized combustion, there is a certain amount of additional air intake such as leakage air and cooling air in the furnace. During operation, these unorganized intake air must be controlled within a certain range in order to carry out organized distribution reasonably and effectively. Wind; too much unorganized additional air intake will change the distribution of air powder in the furnace, and make the excess air in local areas such as the main combustion area and burnout area deviate from the design state, thereby causing the boiler NOx emissions to increase; In the case of low air volume, excessive unorganized air volume will also reduce the organized air distribution volume of the nozzle. Therefore, the air speed of the nozzle will decrease, and the penetration ability of the secondary air will weaken, which will affect the mixing of air and powder in the furnace, resulting in a reduction in the combustion efficiency of pulverized coal and steam The temperature rises and the amount of desuperheating water increases; therefore, it is of great significance to find and eliminate excessive unorganized air intake in the furnace for optimizing boiler combustion

[0004] The unorganized air intake of the furnace generally enters the furnace through the fire hole, manhole door or inspection hole; in addition, in order to adjust the reheating steam temperature and eliminate the residual rotation of the furnace outlet airflow, the tangential combustion nozzle is usually designed to swing vertically or horizontally, There is a certain gap between the air duct and the nozzle, and the hot air in the bellows enters the furnace through these gaps, forming an additional air intake for the nozzle; although the additional air intake objectively plays the role of cooling the nozzle and the air duct, too large a gap will also cause Detrimental effect on the organized air distribution of the nozzles

At present, the air volume distribution of the burner nozzle is realized by adjusting the opening of the baffle on the corresponding air duct and maintaining an appropriate air box-furnace outlet differential pressure. During the operation of some tangential coal-fired boilers, the air box-furnace outlet differential pressure deviates more from the design value. Many, when the boiler is under low load, it is even impossible to establish a reasonable bellows-furnace outlet differential pressure, which shows that the actual air distribution in the furnace deviates from the design state; among them, the unorganized additional air intake is too large is one of the important reasons

[0005] The furnace of modern large-capacity boilers has good tightness, and the air leakage through the manhole door and the fire hole is usually below 5%; while the additional air intake of the tangential combustion swing nozzle is related to the size of the leakage gap, which is affected by the quality of the installation and varies with time. At present, there is no report on the measurement or evaluation of the additional air intake of the swing nozzle, and the evaluation of the additional air intake of the tangential combustion swing nozzle is relatively important for the combustion diagnosis and optimization in the furnace and the evaluation of the installation quality of the nozzle. important meaning

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