A flue based on grid method x Concentration measurement system and method

Abstract

The invention discloses a system and a method for measuring the NOx concentration of a flue based on a grid technology. The system includes sampling pipelines, a switching device, a sample gas sampling device, a sample gas analysis device and a control device, wherein the sampling pipelines corresponding to grid sampling areas one to one; the switching device receives a control instruction from the control device and selects the corresponding sampling pipeline; the sample gas sampling device extracts sample gas from the selected sampling pipeline, and conveys the extracted sample gas to the sample gas analysis device; the sample gas analysis device analyzes the extracted sample gas to obtain sample gas analysis data, and sends the sample gas analysis data to the control device; and the control device calculates the sample gas analysis data to obtain the distribution data of the NOx concentration field at the section of the flue. The system and the method realize the improvement of themeasurement accuracy of the NOx concentration.

Description

technical field [0001] The invention relates to the technical field of flue gas denitrification, in particular to a grid-based flue NO x Concentration measurement system and method. Background technique [0002] In recent years, with the increasingly serious environmental pollution, the state has issued a series of policies and measures to encourage thermal power plants to implement ultra-low emission transformation. x Emission concentration is required to be controlled at 50mg / Nm 3 the following. In the Beijing regional standard, NO is required x Emission concentration is required to be controlled at 30mg / Nm 3 Next, with the improvement of environmental governance and protection, emission standards will be further improved, and other provinces are also demonstrating the work of raising emission standards. Due to the current NO x The concentration is low, the distribution is uneven, and the outlet discharge is low. Therefore, in order to achieve stable and efficient de...

AI Technical Summary

Problems solved by technology

Although the measurement deviation becomes smaller, the SCR system inlet NO x The concentration measurement data is still not representative, and the mixed concentration data is still difficult to meet the needs of efficient and stable operation of the existing denitrification system

The main reason for this phenomenon is that the straight pipe section before and after the sampling point cannot meet the requirements of 2 times the diameter of the upstream and 0.5 times the diameter of the downstream flue, and the air flow at the sampling point is unstable; secondly, the length of the sampling probe into the flue is generally more than 1 meter. While the flow field in the flue and the NO x The distribution of the concentration field is uneven, and even three sampling points cannot represent the actual concentration of the entire flue section. The ammonia injection control system adjusts the amount of ammonia injection based on the mixed concentration measurement data, which will cause the ammonia / nitrogen molar ratio in some areas to be too large, and ammonia Can not fully participate in the reaction, the escape of ammonia at the reactor outlet exceeds the limit; the ammonia / nitrogen molar ratio in some areas is too small, the amount of ammonia is insufficient, and the NO x Not all can participate in the reaction, and the emission concentration exceeds the standard; in addition, the velocity field will also have a certain impact on the ammonia / nitrogen molar ratio

Images