THE MANUFACTURE AND PROPERTIES OF COKE. n
drawing the coke from the ovens before cooling it off with water. The method of cooling the coke on the inside is hard on the brick composing the interior, but it makes a brighter coke and more comfortable work for the cokers. In so far as it relates to the question of moisture in coke, the product absorbs less moisture when cooled off in the inside than outside of the ovens. i
Some coke holds water to the extent of fifteen to twenty per cent of its own weight. Good fresh coke should not possess much over one per cent of moisture ',
when protected from rain and snow. As it takes about !
fifteen pounds of coke in a cupola to evaporate one pound of water, it is evident that the less moisture a h
coke contains the less fuel required in melting, etc. (
Some firms recognize this factor and build stock houses i,"
so as to keep coke under cover. It is claimed that !M
exposing coke to outdoor weather will reduce sulphur. i^
To what extent this is true has never been demon- if
Coal is sometimes ol such poor quality, or full of (/>'
slate or iron pyrites, that it must undergo a process fj
of washing before it can be charged into the oven to ! \,
be coked. The method of treatment consists in crush- rfe
1 ing the coal, if it is in lump form, so as to make it as [|(j
fine as slack. It is then carried by means of buckets j'K
attached to an endless chain from boat, car, or crushers r,
to tubs of water, so arranged with '' jiggers '' that a constant agitation and flow of water causes the different bodies in the coal to take their place in the water according to their several specific gravities. The pyrites and slate, being heaviest, sink to the bottom, and by a series of jogging tubs through which the coal is passed, the floating bodies — the coal partially freed