PVC Ethylene Oxygen Process Gas Online Analysis System

PVC Ethylene Oxygen Process Gas Online Analysis System

The desulfurization flue gas online monitoring system is composed of a smoke and dust monitoring subsystem; Monitoring subsystem for gaseous pollutants of sulfur dioxide and nitrogen oxides; Composition of the smoke emission parameter monitoring subsystem. By using extraction based continuous monitoring sampling method and on-site continuous monitoring direct measurement method, the concentration of pollutants in flue gas is determined and displayed and recorded as required. At the same time, the system monitors the temperature, pressure, and flow rate of the flue gas in real-time, thereby calculating the real-time emission concentration and total amount of gaseous pollutants and particulate matter in the flue gas.

1、 CEMS installation and specification issues

CEMS outlet installation location:

The position should be selected at the front four times the equivalent diameter of the flue and the back two times the equivalent diameter. If this cannot be met, it should be selected at half the length of the flue. For outdoor installations, a rain shelter should be added. The flow measurement points for desulfurization CEMS raw and clean flue gas are: the clean flue gas is slightly larger than the raw flue gas, and there is an oxidation fan blowing air inside the tower in the internal circulation, while the external circulation is basically similar to the two.

The national standard specifies the monitoring locations for CEMS:

Installation location of particulate matter CEMS

1. The particulate CEMS should be installed in representative locations that reflect the condition of particulate matter, and must be prioritized for installation in vertical pipe sections.

2. Located downstream of all particulate matter control equipment and with no air leakage at the monitoring location.

3. The particle CEMS measurement position based on optical principles does not have water droplets or mist, and is not affected by light

4. Easy for daily maintenance, easy to access installation location, sufficient space for cleaning optical lenses, checking and adjusting optical path accuracy, testing instrument performance, and replacing components.

5. The measurement position should avoid the bends and sections of the flue, and be set at a distance of not less than 4 times the diameter downstream of the bends, valves, and reducers, and not less than 2 times the diameter upstream of the above components. When the installation position cannot meet the requirements, a section with stable airflow should be selected as much as possible, but the length of the straight pipe section before the installation position must be greater than the length of the pipe section after the installation position.

Frequently Asked Questions

1) Why is oxygen content measured in CEMS?

This is an environmental requirement, and the concentration of SO2 must be converted to 6% oxygen content before efficiency can be calculated. The purpose of measuring oxygen content is to determine the excess air coefficient of flue gas, in order to facilitate the calculation of the converted SO2 concentration

2) Is there a large fluctuation in SO2 at the outlet of the clean flue gas?

Mainly due to large fluctuations in dust concentration. Due to the high moisture content in the export, it affects the measurement results of dust.

Generally, SO2 fluctuations, if measured directly, may be due to unstable flow velocity. If it is a sampling, it is necessary to check whether the sampling flow rate in the sampling system is unstable, whether there is dust accumulation in the measuring tank, whether the flue gas pretreatment part is damaged or aged, and whether the temperature and pressure compensation in the measuring tank is poor, etc. Regarding oxygen and SO2, fluctuations can sometimes occur due to two processes: blowback and automatic instrument calibration. Suggest appropriate changes in the logic of thermal engineering to maintain oxygen and SO2 values during these two processes.

3) At present, the methods for measuring flow velocity in CEMS are designed based on the pitot tube principle, which measures the dynamic pressure difference of flue gas and calculates the flow velocity according to the formula. Generally, flow velocity measurement and transmission are achieved on site through a differential pressure transmitter installed at the head of the pitot tube. This measurement method requires high stability of the flue gas flow field, and if conditions permit, it must be installed according to regulations.