Cooking liquor is a solution used for pulp preparation, which can dissolve and decompose non-cellulose components such as lignin and hemicellulose in wood or other fiber raw materials, so as to obtain cellulose as a raw material for pulp. The general preparation method of cooking liquid is as follows:
Select appropriate chemicals and dosage: The main components of cooking liquor include lye and sulfuric acid, and different chemicals and dosage can be selected according to different fiber raw materials and production requirements. For example, for cork materials such as pine and spruce, sodium bicarbonate (NaHCO3) or sodium hydroxide (NaOH) is often used as lye, and sulfuric acid is used as a catalyst. Usually, the amount of lye added is 2-4% (on a dry basis) basis), the amount of sulfuric acid added is 1-3% (on a dry basis).
Adding chemicals to the digester: Add appropriate amount of lye and sulfuric acid to the digester, and determine the amount according to the type and quality of the fiber raw material.
Add water and fiber raw materials: Add a certain amount of water and chopped fiber raw materials into the digester, usually the amount of water added is 4-6 times (on a dry basis), that is, 4-6 times the dry weight of the fiber raw materials 6 times.
Carry out cooking operation: seal the digester, and carry out cooking operation under high temperature and high pressure conditions. The cooking time and temperature should also be determined according to the type and quality of the fiber raw material, usually the cooking time is 2-6 hours and the temperature is 160-180°C.
Filtration and washing: After cooking, the cooking liquid needs to be filtered to remove water-insoluble impurities, and then the pulp is washed repeatedly with water to remove residual chemicals in the cooking liquid.
The following is a common method of determination:
Take an appropriate amount of sample, add a certain amount of acid-insoluble lignin extract, put it into a Water Bath to heat and react to make it fully extracted.
Centrifuge after cooling, take the supernatant, add sulfuric acid and concentrated ammonia water to stabilize the pH value at about 2.0, and let it stand for a period of time to fully analyze the precipitate.
The supernatant was filtered off, and the precipitate was washed with water to neutral pH.
The precipitate was re-extracted twice with ethanol/chloroform mixed solution (1:1), centrifuged, and the supernatant was evaporated to obtain pure acid-insoluble lignin.
The obtained acid-insoluble lignin samples were measured by ultraviolet absorption spectrum under certain conditions. According to the absorbance value under different conditions, the content of acid-insoluble lignin can be calculated by methods such as standard curve.
NBCHAO reminds you: During the measurement process, you should avoid the influence of oxygen, sunlight and high temperature in the air on the results, and at the same time pay attention to safe operation to avoid chemicals that cause harm to the human body.
