Thermal power generating unit and denitration control method and system based on NH3 measurement

Abstract

The invention discloses a denitration control method based on NH3 measurement. The denitration control method comprises the following steps: acquiring NH3 measurement values of a plurality of measurement points in a flue, controlling an ammonia spraying amount of an area corresponding to the flue according to the NH3 measurement value, calculating a PID feedforward value according to a preset broken line function, and controlling an NOx concentration of a denitration outlet according to the PID feedforward value. The invention further discloses a denitration control system based on NH3 measurement and a thermal power generating unit comprising the denitration control system based on NH3 measurement. According to the denitration control method based on NH3 measurement, through multi-measuring-point NH3 parameter monitoring, a basis can be provided for an operator to adjust the opening degree of the ammonia spraying valve, so that the ammonia spraying amount of each area is more reasonable, the problem of excessive spraying or insufficient spraying of NH3 is effectively prevented, and the occurrence of blockage of an air preheater can be effectively reduced, meanwhile, the PID feedforward value is introduced into the denitration control system, so that the control reliability of the denitration control system can be effectively improved, and the environmental protection reliability is improved.

Description

technical field [0001] The invention relates to the technical field of thermal power generation, in particular to an NH-based 3 Measured denitrification control methods. The present invention also relates to a kind of based on NH 3 measurement of the denitrification control system and includes the NH-based 3 Measurement of the denitrification control system of the thermal power unit. Background technique [0002] As the country's environmental protection requirements become more and more stringent, thermal power unit emission reduction is as important as safe operation. In order to control NOx emission indicators for thermal power units to achieve ultra-low emissions (ultra-low emissions: that is, to retrofit coal-fired thermal power units and increase denitrification device, desulfurization device, and dust removal device, the concentration of pollutants in the flue gas discharged into the atmosphere by the unit is up to the standard, and the NOx emission index in this c...

AI Technical Summary

Problems solved by technology

However, currently, for NH in the flue 3 The detection generally adopts single-point monitoring NH 3 , the installation method is mostly diagonal installation, the installation method is as follows figure 1 as shown, figure 1 A kind of NH disclosed in the prior art 3 Schematic diagram of the installation of the detection device; this sampling point is not of reference significance for the large cross-section flue, and cannot provide an accurate, true and effective ammonia escape value (ammonia escape: for coal-fired thermal power units, after the denitrification system is put into operation, after Excess NH after denitrification reactor 3 Concentration, NH after denitrification and ammonia injection 3 The ammonia content is the escape of ammonia (required 3 Most of the detection devices use in-situ laser measurement methods. Due to the high concentration of smoke in the flue, the laser cannot penetrate the smoke. Although the site has been installed diagonally, there is often no NH 3 data output, and the original NH 3 The measurement optical path of the instrument is short, and the sensitivity can only reach about 1ppm, which can no longer meet the needs of field process NH 3 The monitoring accuracy requirement for concentration less than 3ppm, at the same time, the original NH 3 The maintenance of the device is large, and the maintenance is very troublesome, and it is often necessary to align the light (on-site vibration and unit load changes may cause the optical path of the instrument to deviate); in addition, the original single-point measurement of NH 3 , cannot reflect the NH in the whole flue 3 content, and cannot provide operators with NH in the flue gas 3 The distribution of the flow field, and the amount of ammonia injection in the flow field cannot be adjusted through the ammonia injection leveling valve, resulting in NH in some areas of the flue 3 Overspray, some areas NH 3 Under-spray, resulting in NOx can not be accurately controlled, resulting in instantaneous excessive emissions

[0004] Therefore, how to avoid due to the inability to accurately measure the NH 3 As a result, the emission of NOx cannot be accurately controlled, which is a technical problem that those skilled in the art need to solve

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