Boiler nitrogen oxide online monitoring system

Project  background

Nitrogen oxides mainly include N2O, NO, NO2, N2O3, N2O4, N2O5 and so on. Among them, the nitrogen oxides formed during the combustion process are almost all N0 and NO2, and these two nitrogen oxides are usually called NOX. At present, among the nitrogen oxides produced by natural mineral dyes such as coal, natural gas and heavy oil, NO accounts for about 90%, and the rest is NO2.

The harm of nitrogen oxides is huge: (1) Endanger the health of people. (2) Harm the growth of forests and crops. (3) Significant impact on global climate change and severe damage to the high-altitude ozone layer.

Known from the formation principle of flue gas pollution components, oxygen is its key component. In the actual production process, when the boiler is burned with fuel, excess air is generally added. On the one hand, the fuel can be fully burned, but another problem also arises. The concentration of pollutants discharged from the exhaust pipe produces "dilution", which greatly Reducing the emission concentration will cause the pollutant emission concentration to reach the “false” standard. Excessive air causes the furnace temperature to drop, which not only affects the combustion, but also takes away a lot of heat and dust, increasing the calculation result of the pollution emission concentration. At the same time, the large air volume also increases the power consumption of smoke exhaust. Controlling the oxygen content of flue gas is very important for controlling the combustion process and achieving safe, efficient and low-pollution emissions.

The emission concentration of sulfur dioxide and nitrogen oxides in the flue gas should be converted according to the specified excess air coefficient, and the size of the conversion value depends on the measured value of the flue gas oxygen content. Therefore, the oxygen content in the flue gas is controlled during operation. Controlling the final emission concentration of pollutants is crucial. A flue gas analyzer is usually used to monitor the oxygen content in the flue gas. The core technology for detecting gas is a gas sensor. At present, electrochemical sensors are widely used.

Design monitoring items: detection of NOX, O2, optional monitoring of SO2, CO, CO2, etc.

Scheme details

First of all, through front-end dust filtration, cooling, water vapor separation through the pretreatment system condenser, and measuring the content of NO, NO2, O2 with a composite gas detector; then according to the provisions of GB5468 or GB/T16157, the atmospheric pollutant reference content Oxygen emission concentration conversion method, conversion of nitrogen oxide emission concentration. The measured gas concentration is displayed on the display screen in real time, and the data signal is transmitted to the terminal such as PLC or computer. It can also be transmitted to the cloud server through wireless GPRS or network, or connected to the environmental protection bureau through the data acquisition instrument for real-time supervision.