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* 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 checkerwork 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 ? 
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. Itseems 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 * and Warren‘ 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 
1 Newberry, S. B., U.S. Patent No. 1,121,532. 3 U.S. Patents Nos. 1,123,841 and 1,124,238. 
2 Newberry, S. B., U. S. Patent No. 1,150,295. 4U.S. Patent No. 1,123,964. 
