Overview of the contact adsorption drying
    In general , the contact group adsorption drying is to dry the adsorbent material and being mixed together, the mass transfer process , and then the two are separated , the solid adsorbent is regenerated and then returned to the drying process. Contact adsorption drying process can be coupled together by the two basic , ① the conventional contact drying , hot solid surface heat conduction ; ② adsorption drying ( also called " desiccant " ) , with the adsorbent material to be dried there is a concentration gradient of moisture , thereby performing the mass transfer process .
    According adsorbent whether as an integral part of the dry product , we can simply divided inert adsorbent and activated two kinds . After drying inert absorbent , the product to be separated . Molecular sieves, zeolites , activated carbon , bentonite , silica gel is a typical inert absorbent . Active adsorbent such as starch , peat , bran , rice straw , cellulose, Mai Su , corn flour, potato starch, beet pulp , fruit plants and oils , vegetable ( such as hay ) cut green stalk can be used as product an integral part , without separation . Also , the dry product can be used as active adsorbent . Obviously, the adsorbent can easily regenerate and reuse , is a measure of the contact adsorption drying technical soundness of the important conditions .
    Using active adsorbent , especially for the contact material and the biological adsorption drying of biological products , as it drops into the drying process the solution was dried by the same moist capillary - porous body , which facilitates the use of convective drying advantageous feature of certain solids ( such as drying the wet bulb temperature ) . Thus, for contacting the solid adsorbent adsorption drying operation has two basic functions .
    ( 1 ) the suspension is dried from most of the water adsorbed . Because water from the capillary - porous body evaporates , replacing the droplet evaporation , thus changing the heat and mass transfer characteristics .
    ( 2 ) changes into the physical structure of the material in the dryer - from the suspension to the multi-component mixture of particulate materials.
    While these two functions are inseparable , but when the suspension is dried in contact with the adsorbent with the body ( and simultaneously partial evaporation of the moisture adsorbing process ) , mainly attributable to the first function simulation .