1. Regeneration of silica gel after absorbing water
After silica gel absorbs moisture, it can be removed by thermal desorption. There are many heating methods, such as electric furnace, flue waste heat heating and hot air drying. The temperature for removing the additional heat should be controlled at 120-180℃, and for the blue gel indicator, discoloration silica gel, and blue silica gel, the temperature should be controlled at 100-120℃. The maximum temperature during regeneration of various industrial silica gels should not exceed the following limits:
The coarse-pored silica gel shall not be higher than 600℃;
The fine-pored silica gel shall not be higher than 200℃;
Blue glue indicator (or discoloration silica gel) shall not be higher than 120℃;
The silica-alumina glue shall not be higher than 350°C.
After regenerated silica gel, its water content is generally controlled below 2% before it can be put into use again.
2. Regeneration of silica gel after adsorbing organic impurities
A. Roasting method
For coarse-pored silica gel, it can be placed in a roasting furnace to gradually increase the temperature to 500-600℃, and it will take about 6-8 hours to reach
The rubber particles are white or yellow-brown. For fine-pored silica gel, the firing temperature cannot exceed 200°C.
B. Rinse method
The silica gel is adsorbed in saturated water vapor to reach saturation and then immersed in hot water for rinsing. It can be combined with detergent to remove waste oil or other organic impurities, and then washed with clean water and dried and dehydrated.
C. Solvent flushing method
According to the type of organic matter adsorbed by the silica gel, an appropriate solvent is selected to dissolve the organic matter adsorbed in the silica gel, and then the silica gel is heated to remove the solvent.
3. the problems that should be paid attention to in the regeneration of silica gel
A.When drying and regenerating, pay attention to increasing the temperature gradually, so as to avoid violent drying causing the rubber particles to burst and reduce the recovery rate.
B.When calcining and regenerating silica gel, too high temperature will cause changes in the pore structure of silica gel, which will significantly reduce its adsorption effect and affect its use value. For blue gel indicator or color-changing silica gel, the temperature of desorption and regeneration should not exceed 120°C, otherwise the color development effect will be lost due to the gradual oxidation of the color developer.
C.The regenerated silica gel should generally be sieved to remove fine particles to make the particles uniform.
Storage and packaging
Silica gel has strong moisture absorption capacity, so it should be stored in a dry place with a shelf between the package and the ground. Packaging materials include steel drums, paper drums, cartons, plastic bottles, polyethylene plastic composite bags, flexible container bags, etc. Avoid rain, damp and sun during transportation.
Silica gel can be used as a desiccant and can be reused. Silica gel is a porous material with different particle sizes formed by proper dehydration of silicic acid gel mSiO2·nH2O. It has an open porous structure, a large specific surface (surface area per unit mass), and can adsorb many substances. It is a good desiccant, adsorbent and catalyst carrier. The adsorption effect of silica gel is mainly physical adsorption, which can be regenerated and used repeatedly. Add acid to the alkali metal silicate (such as sodium silicate) solution to acidify it, and then add a certain amount of electrolyte to stir to form a silicic acid gel; or add acid or Ammonium salts can also generate silicic acid gels. Let the silicic acid gel stand for a few hours to age it, then wash it with hot water to remove the soluble salts, dry it at 60-70°C and activate it at about 300°C to obtain silica gel. The silicic acid gel is soaked in the cobalt chloride solution and then dried and activated to obtain the color-changing silica gel. When it is used as a desiccant, it is blue before absorbing water, and turns red after absorbing water. From the change in color, we can see the degree of water absorption and whether it needs regeneration treatment. Silica gel is also widely used in steam recovery, petroleum refining, and catalyst preparation.
The silica gel of the exhaust gas can be used in the production of water glass.