Pollution source flue gas online monitoring equipment is mainly composed of sampling subsystem, pretreatment subsystem, gaseous pollutant monitoring subsystem, particulate matter monitoring subsystem, flue gas parameter monitoring subsystem, data acquisition control subsystem, auxiliary system and station building.

1. Sampling subsystem

The gas sampling probe is a part that is inserted into the flue gas collection point to collect sample gas. The sampling probe device has electric heating and heat tracing function, which can heat by itself and implement temperature control. The device is suitable for continuous collection of gas samples after the combustion process.

2. Pre-processing subsystem

The flue gas pretreatment system is used to complete the purification, dust removal, dehumidification, and drainage of the sample gas, which improves the reliability, stability and repeatability of the test results of the system, and reduces the operation and maintenance cost.

3. Gaseous pollutant monitoring subsystem

Infrared gas analysis system has high reliability and sensitivity, especially each gas has its own characteristic spectrum, which is not interfered by gas. An analyzer can measure gases including SO2, NOX, CO, CO2, O2, etc.

4. Particulate matter monitoring subsystem

The particle monitoring system uses the laser backscatter method to measure the concentration of smoke and dust.

5. Flue gas parameter monitoring subsystem

The pitot tube is used to measure the flow rate, the pressure sensor is used to measure the pressure, the temperature sensor is used to measure the temperature, and the flue gas humidity is measured by the high temperature capacitive humidity sensor.

6. Data acquisition, transmission and control subsystem

It is composed of data acquisition instrument, industrial computer, display and system software. The main work of the data acquisition instrument is to finally collect and store the analysis results of each analyzer and display it in real time on the industrial computer screen, generate charts, and accept the access of the data acquisition and transmission instrument to provide on-site data.

The industrial computer can automatically perform calibration and system purging, and the sampler temperature, heat tracing tube temperature, condenser temperature and other parameters are included in the system control to ensure that the system is in the best operating state.

7. Auxiliary system

The auxiliary system consists of a power supply system, a lightning protection system, etc.

The automatic monitoring system adopts a dual power supply system and is equipped with a UPS stabilized power supply. The lightning protection system adopts a special industrial lightning protection device with two-level lightning protection measures.

8. Monitoring station

Build special station buildings for monitoring systems in accordance with national standards.

Common faults and solutions

Pretreatment system

1. The sampling probe has a short service life because of the wrong material. 316L should be used.

2. The sample gas pipeline is easy to be corroded. The reason is that the heating effect is not good. Check the heating system; or the pipeline material is wrong, replace it with 316L.

3. Long time no drainage or low drainage, the reason is the failure of the peristaltic pump, check and repair or replace.

4. The sample gas flow is low, it may be that the filter, solenoid valve or pipeline is blocked, check and dredge; or the sampling pump is faulty, check, repair or replace.

5. If the filter paper of the mist filter changes color, the filter element should be replaced in time; if the color changes quickly, the sampling filter at the front should be replaced.

6. There is water vapor in the pipeline behind the cooler. Check whether the cooler is normal, whether the peristaltic pump is normal, and whether the drainage is unblocked.

Analysis system

1. The indication of SO2/NOx is low. Check whether the indication of O2 content at this time is within the normal range of 2% to 8%. If it exceeds, it means that there is a leak in the pipeline, check the air tightness, and eliminate the leak; if the O2 content indicates normal, use the standard gas to calibrate the analyzer;

2. The SO2/NOx analyzer drifts too much during calibration. Check whether the calibration gas is expired and whether the instrument power supply voltage is normal;

3. After each back-purge, the SO2/NOx analyzer indicates low, indicating that the purge air contains water, and the compressed air should be kept dry;

4. If the dust meter misinforms, check whether the fuse of the meter is blown, whether the lens is dirty, and whether the bulb and transformer on the transmitting end are in good condition;

5. The indication of the NH3 escape analyzer is too large. Generally, the calibration gas should be used first. If the meter is correct, check the denitration process, whether the ammonia dosage is too large or the desulfurization tower reaction status is poor, resulting in excess ammonia, etc.; if the analyzer If there is no indication, check whether the transmitter and receiver of the meter are aligned.

Data acquisition and communication system

Common faults of data acquisition and communication systems are inaccurate data, poor communication, data loss, etc. Generally, check whether the insulation of the cable meets the requirements, whether the wiring terminals are loose or corroded, whether water enters the wiring terminals, and the working environment Whether there is strong electromagnetic interference, whether there is vibration in the installation position, whether the communication module or interface is in good condition, etc.

Flue gas refers to the waste gas produced by an enterprise during the production process. The disorderly discharge of flue gas is one of the important factors that cause air pollution. At present, industrial flue gas is generally treated with desulfurization and denitrification technical measures to achieve up-to-standard emission, so as to protect the environment and realize the harmonious development of man and nature.

Therefore, online monitoring of flue gas is a very important means. The CEMS (Continuous Emission Monitoring System) system refers to a device that continuously monitors the concentration and total emissions of gaseous pollutants and particulate matter emitted by air pollution sources and transmits the information to the competent authority in real time. It is called “flue gas online monitoring equipment”.