RECOVERY OF POTASH IN THE CEMENT INDUSTRY. 21 



with the sprays. Steps are now taken to recover the potash, but 

 further details of the operation are held confidential. 



Extensive experiments on a wet process for the recovery of potash in 

 cement dust have also been made at the plant of the Sandusky Cement 

 Co. One method of procedure as outlined in a patent 1 granted to 

 the president of this company has for its object the recovery of the 

 water-soluble potash in the dust. This is done (1) by causing the 

 gases to pass over water contained in shallow vessels in which the 

 solution of alkali salt is produced and replaced as it becomes satu- 

 rated, or (2) by causing the gases to pass upward through a tower 

 filled with an open checker work of brick at the top of which a spray 

 of water is introduced. The flue is so adjusted that most of the 

 water is evaporated in its descent over the extensive brickwork surface 

 in contact with the gases and a small stream only of a concentrated 

 salt solution is discharged continually at the bottom of the tower. 



In a process described in the specifications of a subsequent patent 2 

 provision is also made for the recovery of the insoluble potash in the 

 dust and for utilizing the waste heat of the gases. This is done by 

 passing the gases first through suitable dust chambers and then suc- 

 cessively through a boiler and economizer system before passing into 

 the spray system as outlined in the preceding patent. The dust 

 which is deposited in the connecting flues of the system and the 

 mud which settles out from the concentrated salt solutions are then 

 returned to the kilns for the purpose of volatilizing the potash pres- 

 ent with a view to its ultimate recovery in soluble form. The experi- 

 ments on the commercial application of the methods outlined in 

 these patents have not yet been completed. It seems doubtful, how- 

 ever, from observations made in various industries on the use of spray 

 washers for the purification of gases from a suspended fume, whether 

 any wet process will prove as effective as the electrical process for the 

 recovery of potash from cement flue dust. 



The recovery of potash from feldspar by use of the latter in the 

 manufacture of cement has recently been investigated on a commer- 

 cial scale by the Buffalo Potash & Cement Corporation, operating 

 under the Brown 3 and Warren 4 patents. 



In the process outlined in these patents feldspar is ignited in an 

 oxidizing atmosphere with a sufficient quantity of calcium chloride 

 to furnish sufficient chlorine to combine with the potassium in the 

 feldspar and with a sufficient quantity of calcium carbonate to bring 

 the lime content of the resulting material up to 40 to 55 per cent. 

 The charge is burned in a modified type of copper blast furnace at a 

 temperature practically the same as that required in Portland-cement 

 practice with rotary kilns. Under the conditions of the operation the 

 charge is reduced to a molten mass yielding a cement containing no 



i Newberry, S. B., U. S. Patent *No. 1,121,532. a U. S. Patents Nos. 1,123,841 and 1,124,238, 



2 Newberry, S. B., U. S. Patent No. 1,150,295. * U. S. Patent No. 1,123,964. 



