How to improve the accuracy and precision of the determination of carbon dioxide in cement
Determination of carbon dioxide in cement is generally referred to GB/Tl76-2008 "Chemical Analysis of Cement", and the detection of carbon dioxide is mainly based on asbestos absorption weight method. If this method is used improperly in the process, it will cause some errors. At this time, if we can understand the precautions and operating points in the cement measurement experiment, it will greatly reduce the error in the determination of carbon dioxide in cement.
Principle of the method: The sample is decomposed with phosphoric acid. Carbon dioxide released by decomposition of carbonates is carried by a stream containing no carbon dioxide into a series of U-shaped tubes. Hydrogen sulfide and water are removed first, and then absorbed by alkali asbestos. Carbon dioxide is determined by weighing. content. In addition, in agriculture, we use a dedicated CO2 monitor to monitor the amount of carbon dioxide in the air. At this point it uses carbon dioxide sensors to sense the concentration of carbon dioxide.
In the experiment, the general carbon dioxide concentration measurement steps are six steps of pumping, air purification, acid decomposition reaction, gas purification, and carbon dioxide quantitative absorption and protection. The measurement procedure for the sample is: 1. Remove carbon monoxide and moisture from the device; 2. Constant U-tube; 3. Test sample; 4. Blank test; 5. Continuous measurement and reaction bottle treatment. Specific experimental operations, as long as in accordance with the relevant experimental instructions, can be easily completed. However, during the operation, it is necessary to pay attention to the following problems, which are not encountered when carbon dioxide is measured in the air using a carbon dioxide recorder. This is also a great benefit of the instrumental methods such as carbon dioxide recorders. Points to note: 1) Reaction bottle: Wash and dry before use. Do not heat at a high temperature on the electric furnace to prevent deformation of the reaction flask. After a period of use, the contents of the inner wall of the bottle are washed with dilute hydrochloric acid solution or dilute sodium hydroxide solution. 2) Condensation tube: When the sample is continuously measured, if there is more condensation at the upper end of the condensation tube, the condensation tube needs to be replaced. 3) Clean the U-shaped pipe and the grinding mouth of the absorption tower with a filter paper and apply a small amount of thin layer of Vaseline to ensure the sealing effect. Vaseline do not leak on the surface of the u-shaped symbol to avoid changes in the quality of the u-shaped tube; vaseline should not be too much, so as not to block the inlet and outlet; vaseline of the reaction bottle 4 do not paint Vaseline, because it is a heated part, Vaseline easily heated carbonization . 4) After each time the U-tube and the absorption tower are loaded with reagents, a small group of cotton shall be put on the reagents and at the inlet of the absorption tower at the bottom to prevent the reagents from flowing to block the entrance and exit of the caverns. 5) Magnesium perchlorate, alkali asbestos, and sodium right ash are highly susceptible to water absorption and carbon dioxide. Rapidly make the reagent or add to the drying tube. Close the piston or grinding mouth after installation; immediately after the reagent bottle is used. Sealed, to avoid long-term exposure to the atmosphere and reagent failure. 6) U-shaped symbols should be handled with care, and the u-shaped symbols to be weighed should be placed in a clean, dry porcelain dish to prevent changes in quality after contamination. 7) When disassembling the U-shaped tubes 11 and l2, gloves should be worn to prevent sweat from contaminating the u-shaped tube. Be careful not to apply excessive pressure on the U-shaped tube inward or outward to prevent the bending part from breaking. 8) Concentrated sulfuric acid emits a large amount of heat in the case of water. When the concentrated sulfuric acid is added to the scrubbing cylinder 8, there should be no water in the bottle. Do not paint Vaseline at the ground, so as not to be carbonized by concentrated sulfuric acid. 9) To stop using the device during the comparative period, clamp the inlet pipe of the drying tower with a water stop clamp, close the grinding plug of the u-tube, and put on an empty dry reaction bottle to prevent moisture in the air and Carbon dioxide enters the device. 10) The device connecting pipe uses Φ6mm silicone rubber pipe, silicone rubber pipe is not easy to aging, long service life.
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