Desiccant Refers to a substance that can remove moisture from moist substances. It is often divided into two categories: chemical desiccants, such as calcium sulfate and calcium chloride, which dry by combining with water to form hydrates; and physical Desiccant such as silica gel and activated alumina, which dry by physically adsorbing water. Moisture control is closely related to product yield. In the case of food, at appropriate temperatures and humidity, bacteria and mold in food will reproduce at an alarming rate, causing food spoilage, dampness and discoloration. Electronic products can also be oxidized by high humidity, resulting in defects. The use of desiccants is to avoid the occurrence of defective products caused by excess moisture.
Static Drying
Definition: A quantitative adsorbent and a quantitative solution are allowed to fully contact for a long time to reach equilibrium. (The liquid or gas to be treated is mixed with the adsorbent, and the liquid or gas to be treated does not flow through the adsorbent from top to bottom. This adsorption operation is called static adsorption.)
Applications:
1. Moisture-proof packaging: cameras and photosensitive materials, precision instruments/electrical appliances, food, medicine, shoes, clothing, leather, weapons, telecommunications equipment, etc.
2. Air dehumidification: home interior cabinets, wardrobes, floors, musical instruments, etc.
Dynamic Drying
Definition: A certain weight of adsorbent is filled into an adsorption column, and a solution of a certain concentration is allowed to flow through at a constant temperature at a constant speed, so as to measure the breakthrough adsorption capacity and equilibrium adsorption capacity. (The liquid or gas to be treated flows through the adsorbent from top to bottom, which is called dynamic adsorption.)
Applications:
1. Air drying: warehouses, ship holds, pharmaceutical factories, precision machinery, electronic equipment manufacturing plants, compressed air, instrument air drying.
2. Industrial gas dehydration and purification: hydrogen, oxygen, nitrogen, chlorine, CO2, acetylene, ethylene, methane, ethane, propane, SO3, SO2, natural gas, coal gas
Physical Adsorption
Desiccant Suitable for preventing instruments, meters, electrical equipment, medicines, food, textiles and other various packaged items from getting damp. Desiccants are also widely used in sea transportation, because goods often become damp and deteriorate due to large temperature changes during transportation. Using desiccants can effectively dehumidify and prevent moisture, ensuring the quality of the goods. 1. Desiccants are used for moisture-proof packaging of bottled medicines and food. Ensure the dryness of the contents and prevent the growth of various miscellaneous molds.
2. Desiccants can be used as general packaging desiccants for moisture-proof purposes.
3. Desiccants can be conveniently placed in the packaging of various items (such as instruments, electronic products, leather, shoes, clothing, food, medicines and household appliances, etc.) to prevent items from getting damp, mildew or rust.
Chemical Adsorption
1. Acidic desiccants: concentrated sulfuric acid, phosphorus pentoxide, used to dry acidic or neutral gases. Concentrated sulfuric acid cannot dry strongly reducing acidic gases such as hydrogen sulfide, hydrogen bromide, and hydrogen iodide; phosphorus pentoxide cannot dry ammonia.
2. Neutral desiccants: anhydrous calcium chloride, which can dry most gases, but anhydrous calcium chloride cannot dry ammonia and ethanol;
3. Alkaline desiccants: soda lime (a mixture of CaO and NaOH, KOH), quicklime (CaO), NaOH solid, used to dry neutral or alkaline gases.
