Application analysis of toxic and harmful gas detectors in industry
1. Gas sensors utilizing physical and chemical properties, such as semiconductor type (surface manipulation type, volume manipulation type, surface potential type), catalytic incineration type, solid thermal conductivity type, etc.
2. Gas sensors utilizing physical properties, such as thermal conductivity, optical drying, infrared absorption, etc.
3. Gas sensors utilizing electrochemical properties, such as constant potential electrolysis, galvanic cell, barrier ion electrode, fixed electrolyte, etc.
Based on the damage, we classify toxic and harmful gases into two categories: combustible gases and toxic gases. Because their nature and damage are different, their inspection methods are also different.
Combustible gases are commonly encountered as hazardous gases in industries such as petrochemicals. They mainly consist of organic gases such as alkanes and certain inorganic gases such as carbon monoxide.
The explosion of combustible gases requires certain conditions, namely: a certain concentration of combustible gas, a certain amount of oxygen, and a source of fire that can ignite them with heat. These are the three essential elements of explosion, and none of them are indispensable. In other words, any of these conditions will not lead to fire or explosion. When combustible gases (steam, dust) and oxygen mix and reach a certain concentration, they will explode when exposed to a fire source with a certain temperature. We refer to the concentration of combustible gases that can explode when exposed to a fire source as the explosion concentration limit, abbreviated as the explosion limit, which is usually expressed in%. In practice, this mixture does not necessarily explode at any mixing ratio and requires a concentration scale.
When the concentration of combustible gas is below the LEL (minimum explosive limit) (lack of combustible gas concentration) and above the UEL (maximum explosive limit) (lack of oxygen), there will be no explosion. The LEL and UEL of different combustible gases are also different, which should be taken very seriously when calibrating instruments. For safety reasons, we should usually announce an alarm when the concentration of combustible gas is at 10% and 20% of the LEL, where 10% LEL is referred to. Make a warning alert, while 20% LEL is called a risk alert. This is also the element of our combustible gas detector, also known as LEL detector.
