SMOKE AND DUST ABATEMENT COTTRELL. 681 



an installation now in operation at the Hooker Electrochemical Co., 

 Niagara Falls, where the exit gases of the chloride of lime factory 

 are freed from their last traces of chlorine by first blowing into them 

 as they travel along finelj^ divided slaked lime and a little farther 

 down the flue recovering this again by the precipitation unit shown 

 in figures 40 and 41. Although the lime thus remains in the gases 

 only a few seconds, it is in such a fine state of subdivision that absorp- 

 tion is complete and the gases leave the treater without a trace of 

 odor. 



Still another application, which in a sense is almost the reverse 

 of this procedure, has been worked out in connection with the drying 

 of solutions and emulsions, such as milk and other unstable material, 

 by atomizing them in a fine spray into warm dry air and collecting 

 by electrical precipitation the fine dry powder left by the evaporation 

 of the microscopic droplets as they float along. 



ELECTRICAL PRECIPITATION AND ORDINARY COAL SMOKE. 



As to the relation of electrical precipitation to the problem of 

 ordinary coal smoke, it has already been pointed out in the early 

 portion of this article that the mast general solution of the coal- 

 smoke problem lies in better combustion, and that what is here 

 needed is not so much a method for collecting smoke as one for pre- 

 venting its original formation. However, for some time to come, 

 and, in some special cases perhaps permanently, precipitation methods 

 may prove a stepping stone and useful adjunct. For example, in 

 power plants having a high peak load, i. e., a very high power de- 

 mand for a short period of the day as compared with the remainder 

 of the time it is often impracticable to operate over this peak 

 load without producing some black smoke unless a much larger 

 furnace and boiler equipment is installed than is required for the 

 average load. In such cases the installation and operation of precipi- 

 tation apparatus to take care of this peak-load interval may prove 

 more economic than that of the addition of boilers and furnaces 

 otherwise required. The locomotive smoke from railroad round- 

 houses seems another legitimate field until electrification of steam 

 roads in cities shall become more general. Again there are the 

 stacks of certain furnaces in steel works where for metallurgical 

 purposes it has become established procedure (even though we may 

 question the absolute necessity) to carry a smoliy flame for insuring 

 a reducing atmosphere. 



The electrical treatment of this land of smoke presents little new 

 in the way of difficulties from the technical side save in the me- 

 chanical details of removing the light fluffy soot from the electrodes 

 after deposition. Figures 42 and 48 show two installations for this 



