OBJECTIONABLE FEATURE OF DRYERS. 187 



Fettback has analyzed the gases of this dryer, in order to make 

 sure that they are supersaturated with moisture. By observing 

 the temperature shown on the moistened thermometer and that 

 of the dry thermometer, and also the pressure indicated on a 

 barometer, it becomes possible to ascertain the relative hygro- 

 static condition of these gases. Specially arranged diagrams 

 showed the influence of the volume of the cossettes to be dried 

 upon the final temperature of the gases and also their relative 

 moisture. 



When there are defects in the dryer they may be noticed by 

 a fall of temperature of the gases and their comparative moist- 

 ure. The regulating of the dryer may, to a certain extent, be 

 done by ascertaining its practical working efficiency, allowing for 

 the utilization of the caloric of the fuel. 



We give herewith the formula proposed by Rydlewski for the Practical work- 

 calculation of the efficiency of a cossette dryer: We may sup- ing of dryer, 

 pose that Q is the weight of the fresh cossettes, and q the weight 

 of the dried cossettes, t the temperature in degrees Centigrade of 

 the moist cossettes, and p the weight of the coal, while c is the 

 number of calories liberated by the combustion of one kilo, of 

 coal. 



Caloric utilized C = [Q - q] [637 t] . 

 Caloric furnished C' = cp. 



~ .. , ffi . 100 x C 



Practical efficiency x per cent. = ^ . 



O 



The application of this formula has given for the Buttner and Objectionable 

 Meyer dryer, as well as for the Petry and Hecking apparatus, feature of 

 an efficiency of 82.04 per cent. This formula enables one to 

 ascertain within what limit it is possible to introduce moist cos- 

 settes into the dryer at a variable temperature, and to what ex- 

 tent temperature has an influence on the efficiency of the dryer. 

 A rise of temperature of 30 to 35 C. means certainly an econ- 

 omy of 5 per cent, in fuel. 



Some objections have been made to the Buttner and Meyer 

 dryer, also to the Mackensen appliance, that there follows an 

 important loss of dry substances carried forward by the hot 

 gases. Some authorities have declared that this loss is 25 per 

 cent, to 30 per cent., and even 40 per cent. This, without 



