RECOVERY OF POTASH I33H THE BLAST-FURNACE INDUSTRY. 17 
frequently led directly to the stoves and boilers without further 
treatment. For further purification of the gases, the practice in the 
United States has been to use washing systems. As a result, the 
greater part of the volatilized potash is now lost in these washers. 
The possible recovery of potash in this industry is therefore depend- 
ent on the substitution of a dry system of purifying the gases for the 
present wet systems. Among the dry systems for cleaning gases 
which give promise of successful application for potash recovery may 
be mentioned the Halberg-Beth, the Cottrell, and the Kling-Weidlein. 
The Halberg-Beth system is based primarily on the filtering of the 
gases through canvas bags, the Kling-Weidlein system filters the 
gases through steel wool, and the Cottrell process removes the solid 
particles by electrical precipitation. In the British Isles a modifica- 
tion of the Cottrell precipitator known as the Lodge electrostatic 
system has been used. 
In the Halberg-Beth system the gases must first be cooled to about 
80° C. If the temperature much exceeds this there is danger of the 
bags scorching, and at lower temperatures proper filtration is ^re- 
vented by the condensation of water vapor on the bags, which are 
likely to be torn by the damp mass of accumulated dust adhering 
to them. After leaving the canvas bags the gas needs no further 
cleaning for use in gas engines. 
The Kling-Weidlein system requires no preliminary cooling of the 
gases. It is claimed to have given satisfactory results at the Ohio 
works of the Carnegie Steel Co., Youngstown, and at the plant of the 
Ford Motor Co., at Detroit. 
The Cottrell process makes use of an intermittent direct current of 
high tension, which imparts a charge to the suspended particles of 
dust, which are, under the influence of the strong electric field, 
driven forcibly against surrounding objects. No previous cooling 
of the gases is necessaiy. The Cottrell system has found very suc- 
cessful application in the recovery of potash in the cement industry, 
and, as applied to the blast-furnace industry, has been running suc- 
cessfully for approximately four years at Dunbar, Pa., on pig iron, 
speigeleisen, and ferromanganese, and for three } T ears at Sheridan, 
Pa., on pig iron and ferromanganese. 
In Table 13 is given a list of blast furnaces in this country and 
in the British Isles where dry cleaners have been installed and the 
systems used. 
Table 13. — Blast furnaces fitted with dry cleaning plants. 
GREAT BRITAIN. 
Type of plant. 
Appleby Iron & Steel Co 
Halberg-Beth. 
Do. 
Baldwins Ltd. Port Talbot 
Barrow Steel & Iron Co. (Ltd.) 
Do. 
Blaenavon Coal & Iron Co. (Ltd.) . . . 
Do. 
Ebb Vale Steel & Iron Co 
Do. 
Do. 
Millom & Askam Iron Co 
Do. 
Do. 
Shelton Iron Co 
Skinningrove Iron Co 
Lodge electrostatic. 
Workington Iron Co 
Experimental electrostatic. 
