Application of Gas Sensors in Disposal of Gas Leakage Accidents
For combustible gas monitoring and alarm
At present, the development of gas-sensing materials makes gas sensors with high sensitivity, stable performance, simple structure, small size, and low price, and improves the selectivity and sensitivity of the sensor. Most of the existing gas alarms use tin oxide plus noble metal catalyst gas sensor, but the selectivity is poor, and the accuracy of the alarm is affected by catalyst poisoning. The sensitivity of semiconductor gas-sensitive materials to gases is related to temperature. The sensitivity is low at normal temperature, and the sensitivity increases with the increase of temperature, reaching a peak value at a certain temperature. Since these gas-sensitive materials need to achieve the best sensitivity at higher temperatures (generally greater than 100°C), this not only consumes additional heating power, but also causes fires.
The development of gas sensors has solved this problem. For example, gas sensors made of iron oxide-based gas-sensitive ceramics can produce gas sensors with high sensitivity, good stability, and certain selectivity without adding noble metal catalysts. Reduce the operating temperature of semiconductor gas-sensitive materials, greatly improve their sensitivity at room temperature, so that they can work at room temperature. At present, in addition to the commonly used single metal oxide ceramics, some composite metal oxide semiconductor gas-sensitive ceramics and mixed metal oxide gas-sensitive ceramics have been developed.
Install gas sensors in places where flammable, explosive, toxic and harmful gases are produced, stored, transported, used, etc., to detect gas content in time and detect leakage accidents early. And the gas sensor is linked with the protection system, so that the protection system will act before the gas reaches the explosion limit, and the accident loss will be kept to a minimum. At the same time, the miniaturization and price reduction of gas sensors make it possible to enter the family.
Detection of gas types and characteristics
After the gas leakage accident occurs, the accident disposal will focus on sampling and testing, determining the warning area, organizing the evacuation of the masses in the dangerous area, rescuing poisoned personnel, plugging, decontamination, etc. The first aspect of disposal should be to minimize the risk of leakage to personnel, which requires knowledge of the toxicity of the leaking gas. The toxicity of a gas refers to the release of substances that can disrupt the normal responses of a person's body, thus reducing the person's ability to develop countermeasures and mitigate injuries in an accident. The National Fire Protection Association divides the toxicity of substances into the following categories:
In case of NH=0 fire, in addition to the danger of general combustibles, short-term contact with no other dangerous substances;
NH=1 short-term exposure to substances that can cause irritation and cause slight harm to humans;
NH=2 High concentration or short-term exposure can cause temporary loss of ability or residual injury;
NH=3 short-term exposure can cause serious temporary or residual injury;
Because toxic gas can enter the human body through the human respiratory system and cause harm, safety protection must be completed quickly when dealing with toxic gas leakage accidents. This requires accident disposal personnel to be able to understand the type, toxicity and other characteristics of the gas in the shortest possible time after arriving at the accident scene.
The gas sensor array is combined with computer technology to form an intelligent gas detection system, which can quickly and accurately identify the gas type, thereby measuring the toxicity of the gas. The intelligent gas sensing system consists of a gas sensor array, a signal processing system and an output system. Multiple gas sensor elements with different sensitive characteristics are used to form an array, and the neural network pattern recognition technology is used for gas identification and concentration monitoring of mixed gases. At the same time, the types, properties, and toxicity of common toxic, harmful, and flammable gases are input into the computer, and an accident disposal plan is prepared according to the nature of the gas and input into the computer. When a leakage accident occurs, the intelligent gas detection system will work as follows:
Enter the site→adsorb gas samples→generate signals from gas sensors→identify signals by computer→output gas types, properties, toxicity and disposal plan by computer.
Due to the high sensitivity of the gas sensor, it can be detected when the gas concentration is very low, without having to go deep into the accident scene, so as to avoid unnecessary harm caused by ignorance of the situation. Using computer processing, the above process can be completed quickly. In this way, effective protective measures can be taken quickly and accurately, correct disposal schemes can be implemented, and accident losses can be reduced to a minimum. In addition, because the system stores information such as the properties of common gases and disposal plans, if you know the type of gas in the leakage accident, you can directly query the gas properties and disposal plans in this system. NH=4 brief exposure can also cause death or serious injury.
