The Bridgeport times and evening farmer., 1918-08-09

ous pig iron. To remove the excess of phosphorous the iron is melted in converters lined with limestone, and quicklime is added. At a certain stage air is driven through the molten ma terial, which leads to an accumula- tion in the slag of the phosphorus
 originally present in the metal. This
 slag Is drawn off and cooled, and when. finely ground is placed on the market under the trade name of ba-
 sic slag. The phosphoric acid in the slag prepared in this way varies from Il to 23 per cent.
 For a long time the fertilizing val
 ue of the slag was not recognized, but
 1t has now become one of the most
 popular of commercial fertilizers. In fact, on account of it's freedom from actdity many prefer it to any other phosphatic material. The slag pro-
 duced for the fertilizer trade amounts to about 100000 tons annually. The third main aveneue for escape
 of waste in the blast furnace is volati-
 lization. These losses in the form of
 gas, dust, and fumes are receiving | special attention at present. In the operation of the modern blast furnace
 a portion of the waste gases is utilized
 directly in gas engines for making
 blast or for generating electric pow
 CT while the remainder is used in
 burning under boilers and tu heating
 stoves for preheating the blast. The
 dust collected in the stoves and boil
 CTS has long been known to have some fertilizing value, but little at-
 tention was given to it until recently
 when it was found that the dust col
 lected in some plants contains some-
 times upward of 20 per cent. of solu-
 ble potash, of great vaalue for 1Ise in l fertilizers
 In an investigation recently made
 at one of the steel plants of this coun-
 try it has been found that the potash
 in the dust collected in the stoves and
 boilers amounts to only about per
 cent. of the total escaping from the
 furnace. The greater part is still lost
 in the washers or escapes from the
 flues- Tests also were made at the
 same plant with an electrostatic or hot dry process for purifying the gas. The results showed not only potash !, but other materials, as iron and zinc , compounds, which may be carried , over in the dust. The possibilities of potash recovery in the steel industry are promising but, owing to the ab- normal conditions now prevailing new I developments are likely to be post poned for the present
 A good illustration of case in ' which a valuable product is lost in , an industry without it being known } for a long time what a waste is &C., 4oI ie, I1 the escape of potash from cement . plants. In the manufacture of Port . land cement an intimate mixture of g s material like clay and limestone k f heated to the point of fusion. Fol l many years it was thought that in the
 manufacture of cement this produc e was the only one produced, and that = therefore, no loss of any other ma r terial took place. It is now knowI 6 however, that in the burning of ce = ment the potash in the raw materials l, escapes from the kilns with the flu. r dust. Even after it was noticed tha n some loss of potash took place il = this way, little importance was at r tached to the observation until andy y ses were made four or five years az, j. of dust collected at the plant of tn d Riverside Portland Cement Com @ pany.
 y The original object of collecting tn l. dust was to comply with injunction is proceedings instituted by orang If growers against the escape of dus It from the plant. To the surprise 0 d every one the dust when collected wa It found to contain such a percentag
 of potash as to make it's recovery se profitable procedure entirely apar d from any other consideration. Sine is then a number of additional plant al have also installed equipment for col k lecting potash and at, several othe r. plants installations are now buildins o- The recovery of potash at the Riv r. erside plant now amounts to abou