There are numerous types of carbon and sulfur analyzers, each with its own distinct analytical principles, application scope, and price. The following summarizes several commonly used analytical methods:
1. Infrared Absorption Method (Infrared Carbon and Sulfur Analyzer): The carbon and sulfur in the sample are heated to high temperatures in oxygen-rich conditions, oxidizing them into carbon dioxide and sulfur dioxide gases. After treatment, these gases enter a corresponding absorption cell, where they absorb the corresponding infrared radiation. This signal is then transmitted by a detector and processed by a computer to output the result. This method is accurate, rapid, and highly sensitive, and can be used for both high and low carbon and sulfur content measurements. Infrared carbon and sulfur analyzers using this method have a high degree of automation and are relatively expensive, making them suitable for applications requiring high analytical precision.
2. Conductivity Method (Conductivity Carbon-Sulfur Analyzer): This method measures and analyzes carbon and sulfur content based on changes in conductivity. High-temperature combustion of the sample produces a mixed gas that is absorbed by a conductivity cell, causing a change in resistivity (the inverse of conductivity). This method allows the determination of carbon and sulfur content. It is characterized by accuracy, speed, and sensitivity. It is primarily used for the determination of low-carbon and low-sulfur contents.
3. Volumetric Method (Gas Volumetric Carbon-Sulfur Analyzer): Commonly used methods include gas volumetric carbon measurement and iodine titration and acid-base titration for sulfur measurement. Gas volumetric carbon measurement and iodine titration for sulfur measurement are particularly rapid and accurate, making them the most commonly used methods for combined carbon and sulfur determination in my country. Carbon and sulfur analyzers using this method have an accuracy limit of 0.050% for carbon and 0.005% for sulfur, meeting the needs of most applications.
4. Titration Method (Titrator): Non-aqueous titrators use acid-base titration to determine carbon and sulfur in steel. Compatible with electric arc furnaces, it is suitable for general laboratories and furnace-front testing.
5. Gravimetric Method (Combined Carbon and Sulfur Determination): Alkaline asbestos is often used to absorb carbon dioxide, and the carbon content is determined from the "increment." Sulfur determination is often performed using the wet method. The sample is decomposed and oxidized with acid to convert it into sulfate. Barium chloride is then added to a hydrochloric acid medium to produce barium sulfate. After precipitation, filtration, washing, and calcination, the barium sulfate is weighed and the sulfur content is calculated. The disadvantage of the gravimetric method is its slow analysis speed, making it unsuitable for on-site carbon and sulfur analysis in enterprises. However, its advantage is its high accuracy. It is still recommended as a standard method both domestically and internationally and is suitable for standard laboratories and research institutions.
6. For determining the carbon and sulfur content in metals, other methods include ICP, direct reading spectroscopy, X-ray fluorescence, mass spectrometry, chromatography, and activation analysis, each with its own advantages and scope of application.