Minimum drying time

The method gives no information about sohds residence time or dryer length. A minimum drying time can be calculated by evaluating the maximum (unhindered) drying rate assuming gas-phase heat-transfer control and estimating a gas-to-solids heat-transfer coefficient. The simple equation (12-60) then apphes ... 

In the case of solvent-containing adhesives, a minimum drying time has to be provided for. This is particularly applicable if both adherends are impermeable... 

Consider open assembly time, minimum drying time, maximum drying time (Figure 5.2). 

Minimum drying time In the case of solvent-based adhesives, the time period between the adhesive application and the fixing of the adherends, to enable the evaporation of the major part of the solvent from the liquid adhesive film. 

Fluidized bed dryers work best on particles of a few tenths of a mm dia, but up to 4 mm dia have been processed. Gas velocities of twice the minimum fluidization velocity are a safe prescription. In continuous operation, drying times of 1-2 min are enough, but batch drying of some pharmaceutical products employs drying times of 2-3 hr. 

Fig. 1.99.2. Top RM measured by KF as a function of drying time. Ten vials were each closed at the time indicated by mean RM data. The cake from 5-7 vials out of each 10 vials closed was analyzed with 3-5 samples from each vial. The average data shown in the top graph are the mean values of 15 or more measurements. The bars are not standard deviations they mark the minimum and the maximum of all measured data. ( ) Run 1, mean Tice = -38.56 °C, SA = 0.38 °C. (+) Run 2,...

Tsh,MD = 0 °C- Pc = 008 mbar. Tsh,SD = 40 °C Below dW data calculated from DR measurements during secondary drying as a function of drying time. ( ) Mean dW of all three runs bars, minimum and maximum of all calculated dW... 

Minimum pressure at the end of secondary drying Maximum temperature of the condenser Temperature range of the product at the end of freezing Maximum primary drying product temperature Product primary drying time... 

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