The lime trough is also made moveable on a centre or axis, in such a manner that it may readily be inverted by a lever from the outside, for the purpose of emptying its contents into the bottom of an exterior vessel, from which the waste materials may be discharged at pleasure.
With this machine we are farther enabled to employ the purifying mixture in a semi-fluid state, and consequently in a much less bulk; and after having suffered it to remain in the reservoir destined to receive it, the waste substance speedily acquires such a degree of solidity that it may be dug out with a spade and carted away in a small compass. The safety of the apparatus is therefore insured and the construction of expensive drains and sewers is rendered unnecessary. The following description will render the construction of the improved apparatus obvious.
A, A, fig. 2, [plate II.], is a rectangular four-sided prism, made of cast-iron plates, screwed together air-tight with bolts and cement. The base of the prism terminates in a rectangular four-sided pyramid placed with its apex downwards. It is surrounded by an iron stage, supported upon pillars, as shown in the design.
Within this vessel, which in fact composes only the outer case of the apparatus, is contained an oblong trough B, fig. 2, [plate II.], (it is shown in the design as if broken down), moveable upon an horizontal axis, fixed to one of its longest sides, so that by means of the wheel C, or lever communicating with the axis, and applied on the outside of the machine, the trough B, may be inverted, and its contents discharged into the exterior case, or lower part A, A, of the machine. The part B, of the machine is called the lime trough, because it is destined to contain the quick-lime and water, by means of which the crude coal gas is purified. Within this trough B, is inverted an oblong rectangular box D, closed at top and open at bottom, called the air-box, because it receives the gas to be purified.
In each of the longest sides of the box D, are perpendicular openings or slits (as shown in the design) exactly opposite to each other. Through the whole length of this box D, passes a horizontal axis furnished with as many teeth or claws as there are upright openings, through each side of the box. These claws extend a little way through the openings so that when the axis, which passes through a stuffing box, is made to revolve by means of the handle X, the ends of the claws pass through the openings and scrape them out every time the axis is turned. The claws operate first on the openings of one side of the box and then on those on the opposite side. They pass quite through and therefore keep them clear; those parts of the claws which enter into the openings are narrow in the direction of their motion, and that part of each claw which is nearest to the centre, is broad and flat, hence they act as paddles or rowers whilst they are in motion, to stir up the quick-lime and water.
Fig. 10, [plate III.], represents a transverse section of this part of the apparatus. B, B, is the lime trough; D, the air box inverted into the lime trough; the dotted circle shows the sweep of the claws when the shaft is put in motion. The darts show the course of the gas.
Fig. 10, [plate VI.], represents a plan of the machine. G, shows the inverted air-trough with its axis, and the claws or teeth fixed upon the axis. H, is the lime trough. A, the outer case of the machine; R, R, the axis, to which is affixed the wheel or lever, for inverting the trough H. L, the axis and handle to give motion to the shaft upon which the claws are fixed, for stirring up the contents of the lime trough.
The inverted air-box D, fig. 2, [plate II.], is supported within the outer case of the machine A, A, fig. 2, [plate II.], by cross bars, and the axis is put in motion by the handle X, on the outside of the machine. It is rendered air-tight by a stuffing box, and is provided with wheel-work, as shewn in the design, fig. 2, [plate II.], to communicate the motion to the axis.
The gas is brought into the air box by the pipe N, fig. 3, which proceeds from the tar vessel, fig. 3, [plate II.] The gas cannot escape out of the machine without displacing the column of fluid in the lime trough, in order to make its way through the openings or upright slits in the side of the air box D, and thus bubbling up through the mixture of quick-lime and water, the depth of which is one foot. The sulphuretted hydrogen and carbonic acid being thus made to combine with the lime, the carburetted hydrogen is left more or less pure, it is conveyed into the gas metre, by the pipe V, where it is to be measured, and from thence by the pipe W, fig. 4, into the gas-holder.
When the purifying mixture is to be removed, the workman unbolts the wheel C, fig. 2, and turns it half way round; (if the emptying of the lime trough requires more power than can conveniently be applied by means of the wheel, the axis of the trough may be worked with a tooth and pinion, a small wheel being attached to the axis of the pinion as a perpetual handle;) this motion inverts the lime trough B, and its contents become discharged into the outer case forming the inverted pyramid of the apparatus, whence the waste materials may be conveyed into the reservoir or pit Q, by drawing open the sliding valve o, fig. 2, [plate II.], or o, fig. 3, [plate VII.], added for that purpose to the discharging pipe P, fig. 2, [plate II.], or p, fig. 3, [plate VII.] To prevent the air entering into the machine when the waste lime is discharged, the lower extremity of the outlet pipe P, dips into the basin Q, fig. 2, [plate II.], which always contains a portion of the waste fluid and thus seals the extremity of the pipe P.