Author：Alwaysbrong
2024-03-22 04:14
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Online monitoring of smoke has become an important basis for environmental supervision and law enforcement in China. Ensuring the accuracy of online monitoring data is the foundation of scientific and correct law enforcement. In online smoke emission monitoring, smoke humidity is a very important and necessary parameter, which is also the most difficult to accurately measure; The accuracy of this parameter also directly affects the determination and correct enforcement of other components.
At present, various "two high" industries are implementing ultra-low emission control, which has led to a gradual increase in water content in flue gas. Depending on different industries and treatment processes, the humidity range ranges from 8-50 Vol%. The deviation of online humidity monitoring values can cause significant errors in the emission of gaseous pollutants, particulate matter, and total smoke emissions from the entire pollution source, seriously restricting the accuracy of monitoring data. Therefore, whether a humidity of 4 ℃ dew point (0.8 Vol%) -50 Vol% can occur is the primary factor determining whether the humidity generation device is suitable for calibration of flue gas hygrometers.
A humidity generating device is a device that generates constant humidity by utilizing gas-liquid and gas-solid two-phase equilibrium at a certain temperature and pressure. The PreGASS-4500 humidity calibration device of Alwaysbrong Shares adopts the principle of combining isobaric mixed flow method and permeation method. It generates a stable mixed humidity by humidifying through Nafion permeation tube and accurately controlling the flow rate ratio of dry and wet gas. It can simulate the occurrence of high temperature humidity up to 0.8-50 Vol% at 150 ℃. At the same time, high-precision temperature and humidity sensors (mirror dew point meter) are used for traceability calibration.
The key technologies used to achieve stable humidity and high-precision portable devices include:
Wide humidity range and portability
Based on the Nafion permeation tube humidification principle, it can quickly achieve stable humidity based on the set temperature, with humidity occurring within the range of 0.8-50 Vol% and flow rate controlled within 1-5 LPM, while meeting the portable requirements of a total weight of less than 15kg;
Moisturizing is more stable
In the design of a humidified water tank, a specially designed baffle device is used to ensure that the deionized water in the tank is heated uniformly and stably, ensuring that the time required for different humidity conversions is less than 3 minutes, making it suitable for rapid on-site calibration;
High precision humidification
In the design of the mixing box, special baffle plates and control units are also used to make the entire dry, wet, and other standard gases more uniform in the mixing box, thereby ensuring that the humidity generated meets the accuracy requirement of ≤ ± 0.5 Vol%;
Fast humidity response speed
The constant temperature water tank control system adopts a special algorithm based on BP neural network PID control, and the mixed air box humidity adjustment control system adopts a special algorithm based on fuzzy self-tuning PID control, which can better meet the fast response requirements of the humidity calibration device on site.
