CHAPTER XXVI.

Preparation of coal for market.

The demands of consumers for an acceptable fuel for do- · mestic and manufacturing purposes can only be satisfied by a more or less complicated method of preparation which has for its principal objects:

1. The removal of slate, bony coal, rock and other impurities which are present in the coal as it comes from the mine.

2. The assortment of the coal into grades of nearly uniform size.

3. As there is a larger demand for coal of the intermediate sizes than can be supplied from the coal as mined, it is necessary to break up some (or all) of the large lumps to increase the percentage of these intermediate sizes.

All of these objects are accomplished by the process of preparation in the "Breaker." By reference to the next chapter it will be seen that the breaker is a large structure in which the coal is screened over bars, picked, crushed, run through cylindrical screens, and picking shutes, and often washed, before it is finally passed to the shipping pockets.

As it comes from the mine the coal consists of fragments of all sizes, mixed with more or less slate and rock and a considerable amount of coal too fine to be marketed as fuel, and more or less coal known as bony coal, (which contains nevertheless a large percentage of carbon) and lumps of coal with layers of slate adhering to one or both sides, or distributed throughout the lump.

When the mines are very wet, as in the Panther Creek district, the appearance of a car load of coal as it comes from the mine is suggestive of anything but merchantable fuel. It seems to consist of rock, slate, and slaty coal, very

(443 AC.)

little coal being visible, and the whole covered with a black muddy mass of fine coal and dirt, and dripping with dirty

water.

When the colliery from which the coal is mined is opened on a thick bed with a steep dip, all the slate and other refuse is loaded with the coal, but when the bed is thin or the dip is flat, the slate, rock, and much fine stuff are left in the mine, and the coal, as it comes out of the mine, contains . only a comparatively small amount of refuse

To attain the best results at the least cost, and with the least waste, it is evident:

1. That the coal already broken down to a marketable size, say from egg to pea,-should be separated as quickly as possible from the remainder, and

2. That no coal in large lumps containing any layers of slate should be permitted to pass through the rolls.

3. That all bars, screens, and rolls (coal crushers) should be fed regularly and evenly, and not overcrowded.

4. That no coal, rock, or waste should be handled or treated twice over (unless absolutely necessary).

When a mine car comes from the mine it goes directly to the dump, (cradle-dump, tip or tipple,) and the coal is dumped upon a set of inclined bars or into a shute or pocket, from which it is slowly fed under a gate and allowed to slide down over the bars. These bars are placed from three to six inches apart and separate the coal into two portions that are to be separately treated.

That portion passing through the bars is usually conveyed directly to a large but short screen, known as a dirt or mud screen, which separates the fine coal, (pea and smaller sizes,) but it is sometimes hand-picked before passing to this screen.

The broken and egg sizes coming from the mud screen are picked free from slate and sent direct to the pockets for shipment, or sent to the "Pony rolls" or "Monkey rolls" to be broken down into egg, stove, small stove, and chestnut sizes.

That portion passing over the main screen bars, runs out upon the "platform," which is a flat or slightly inclined

floor covered with iron plates, and is cleaned by the platform men.

The slate and rock are picked out and sent down the rock shute, the good lump coal goes to the lump shute, and the "rough coal" (and sometimes a large part of all the lump coal) to the crusher rolls.

The method of preparation will be more fully understood by reference to the diagrams of Atlas Sheet No. XIX. These diagrams show four methods of preparing coal, which differ from each other in many particulars. These differences are mainly due to differences in the character of the coal, the amount of dirt, the wet or dry condition of the coal, etc.

A dozen other diagrams might be prepared of other breakers, no two of which would be exactly similar, but those given will serve to illustrate sufficiently well several prominent and important features. Thus we can readily see the radical difference between the method of preparing the dry clean coal of the Hollenback colliery and the dirty and wet coal at the Lehigh Coal and Navigation Company's mines, and at the same time understand why the systems vary so widely; and between the old style Hammond breaker, where the broken and egg are run completely through the breaker, and other systems where the broken (at least) is taken out at a much earlier stage, and between the plans by which the coal is divided and subdivided and then again mixed together, and the method by which (Cross Creek) after being divided the two parts are never re-united.

Cross Creek Breaker No. 2.

The method of preparing the coal at the Cross Creek Breaker No. 2, (July, 1882,) is shown by the diagram on Atlas sheet No. XIX. At Breaker No. 1 the process is somewhat different, the principal differences being indicated by data inclosed in parentheses on the diagram.

The coal is dumped into a shute from which it is gradually allowed to run down upon the bars under a gate provided with a row of sharp (spike) teeth on its lower edge. This gate has a vertical motion, moving between upright guides, and is operated by a hand lever.

The bars are placed from three to four inches apart, and divide the coal into two portions.

That portion passing over these bars passes on to a set of bars placed about seven inches apart,-these bars forming a continuation of the first sets;-the coal passing over these bars is necessarily of large size, and runs directly out upon the platform. Here the slate and rock are separated by the platform men and the coal is pushed down into the lump coal shute. At the head of this shute another set of seveninch bars is placed; the coal passing over these bars runs down into the lump coal shute to be shipped as lump, while the smaller pieces run through these bars and pass into the steamboat rolls, which crush it down to the size of steamboat and smaller. From these rolls it passes to a shute in which are bars nearly five inches apart which separate out the smaller sizes (but before reaching these bars the slate is picked out) and allows the steamboat to pass over and down into the steamboat shute. The smaller sizes passing through these bars runs into a pair of small rolls, is crushed down to the size of broken and smaller, and passes into the broken screen.

The coal that passes through the first set of seven-inch bars runs into a shute and passes to a second set of bars nearly five inches apart, the slate being picked out on its way down the shute,-the steamboat coal passes over these bars to the steamboat shute, and coal of smaller size passes through to a pair of small rolls breaking it to the size of broken and smaller, and then passes to the broken screen.

The broken screen obtaining coal from the above two sources, separates out broken and egg sizes and all the smaller sizes pass direct to the stove screen.

The broken and egg both pass down picking shutes (“telegraphs") to their appropriate pockets.

The stove screen separates out stove and chestnut sizes, and the smaller sizes pass to the pea screen.

The stove and chestnut both pass along picking shutes on their journey to their appropriate pockets.

The pea screen separates out pea and buckwheat and dirt. The pea and buckwheat sizes both pass to Clark jigs and

from the jigs to the loading pockets, and the dirt (passed through" mesh) goes direct to the dirt pocket and thence to the dump.

The coal that passes through the first set of bars is very dirty. It goes direct to the mud screen which separates,

1. Coal larger than broken; (over 3" mesh ;) this goes to a set of small rolls and thence to the broken screen.

2. Broken and egg sizes (31" to 2") which goes direct to the broken screen.

3. Stove, and smaller sizes going to the stove screen. 4. Pea and smaller.

The stove screen separates stove and chestnut which are both jigged before going to the pockets, and pea and smaller sizes which with the same sizes separated out by the mud screen (4) go to the pea screen.

This pea screen separates in the same manner as the one already described.

The broken screen also separates in the same way and the coal is put through the same process as that already described, the smaller sizes passing successively to stove and pea screens.

Hammond Breaker.

The method of preparing the coal at Hammond colliery given below is condensed from a description by Mr. H. S. Thompson, Mining Engineer for the Girard Estate:

It will be easily understood by reference to Atlas sheet No. XVIII, and to the diagram on Atlas sheet, No. XIX. The letters all refer to the plan and elevation of this breaker shown by the former illustration.

At the Hammond colliery the product of the mine is raised through the slope in small cars, called wagons, which run by gravity from the head of the slope to the breaker tips or dumps, two in number, A, A, where they are dumped and emptied in the manner shown. The empty wagons are pushed back by hand to the foot of the automatic plane B, by which they are raised to a height sufficient to allow them to return by gravity to the head of the slope.

The mixed coal, slate, and dirt taken from the mine enters