US1489378A - Firing with powdered fuel - Google Patents

Description

April 8 1924.

W. R. WOOD FIRING WITH POWDERED` FUEL Filed May l1. 1925 ,m//////////W///// I Patented Apr. td, lge.

WEIRD) RUTHERY "WD, F LN'DQN, ENGLAND.

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Application led May .l, i923. Serial No. 638,357.

ments Relating to Firing with Powdered Fuel, of which the :following is a specification.

burning powdered fuel in a heating furnace such as a boiler furnace and has for its ob- .ject to dry the fuel on its way to the pul-v verizer bymeans of thewaste gases or the furnace.

ln order that the temperature of the furnace gases may be sufficiently under control provision is made for mining air with the turnace gases before they are passed over the fuel. F or it will be obvious that i 2o if the temperature of the coal were raised to that at which incipient carbionizatiou occurs, combustible matter would be lost unless the furnace gases were returned through the :furnace after they had traversed the coal, which would defeat one ot the objects' of 'the invention, namely keepin cutoff' the furnace the water in the fuel. nother object of mixing airl with the 'furnace gases is.

to dilute them in respect of their content oi water vapour, or, in more exact language, to diminish the partial pressure of the water vapour which 'they carry as a productor combustion of the fuel. The lower such partial pressure, the greater the drying capacity of the gases.

Another object of the invention is to avoid the nuisance created by delivering dust laden gases into the atmosphere at 'alow level. :ln passing through the coal to be dried the gases take up 'from the coal a `portion et dust which, although quite small when considered as lost fuel is sutilciently important when considered as dust in discharged gases. rlhe invention avoids this objection by returning the gases which have passed through the fuel, to the flue of the furnace. By this expedient the dust is in part deposited after the manner of Hue dust generally and in part dissipated atehigh level with the main volume of flue gases.

'lfo ensure satisfactory working it is generali best to withdraw the hot gases trom the `ue by means of a fan or the like.

ln the accompanying drawings Fig. l is a diagram representing a boiler furnace inlil This invention relates to improvements in' chamber a and back through the slotted lowstallation to which the invention is applied, and Fig. 2 illustrates a modification.

Referring to F ig. l of the drawings, a indicates a vertically disposed drying chamber, provided with aV centrally disposed -Tf chute .Z extending longitudinally thereof, through which chute the fuel is led to the hopper la of a pulverizer Z. The portion ol the chute Z; within the chamber a is provided with multiple openings,` preferably dened by a series of slats or bars in louver "termation, to admit Afree circulation oivgaseous drying media to and through the chute.

Leading into the upper part of the chamber a is a` pipe e which is connected to the chimney or ilue d ot the furnace or other heating unit in which the fuel is to be burned and near the bottom 'oit the chamber o, there is connecting a pipe e which leads baclr into the chimney or due d, the latter pipe beingprovided with a suction tan g and e regulating damper it., The pipe e is provided with a gate or damper f cooperating with an ,air inlet in the wall ol the ipe, by means of `which an accurately regu ated supplyot air may be admitted to the ipe and admired with the tlue gases or pro ucts of combustion before lthe latter enter the drying chamber. ln order to cause" the mirture of lue gases and tempering air to pass at leastA twice through the body' of fuel being fed through the chute h, a balde c is disposed between the chute and wall et the chamber av and between the discharge end of pipe e and the intake end et' pipe e', so that the gases will pass transversely through the slotted openings in the upper part of the chute and in a reverse direction in the lower part of the chute, as indicated by the arrows. p

The operation of the apparatus is as follows: rThe coal is fed into the top of the drying chamber through the chute 'o and the products of combustion or Jfurnace gases are taken from vthe flue or chimney d through fl the pipe c, delivered into the upper part ol the chamber a, and passed transversely through the openings in the chute d and the fuel in the latter, thence downward in the er end of the chute and the fuel therein to the exhaust pipe e' back to the chimney. The furnace gases would, under ordinary conditions, be ot too high a temperature to l admit to the drying chamber, and would @llt be liable to cause incipient combustion of the fuel and would poibly produce an explosion if any material amount of the fuel were in a highly pulverized or comminuted condition, and in order to prevent these contingencies the temperature of the i furnace gases and any ine'particles of fuel which may be taken up t ereby into the chimney or stack d. .The particular advantages of this coordination of a paratus, are that the fuel will be effective y dried before reaching the pulverizer and the moisture and the drying medium separated, from the fuel and diverted into the chimney or stack, so that neither the moisture content of the fuel nor the furnace gases are delivered, in any appreciable quantities to the furnace, but, on the contrary, the completely dried and pulverized fuel is delivered to the furnace in the best possible condition to effect complete combustion. It will be understood that any appropriate means for feeding the comminuted fuel from the pulverizer to the furnace may be employed and that illustrated in Fig. 1 is merely exemplary, the same comprising a screw conveyer 'm for delivering the pulverized fuel from the pulverizer l to a feed chute n, which latter' is provided with a brushA or similar propellin device p near its lower end which isr e ective in pro'ecting the wdered fuel through the fue opening 0 1n the furnace wall.

Theconstruction shown in Fig. 2 is similarl in -all respects to that illustrated in Fig. 1, except that the suction fan g and the damper hf are located in the pipe e supplying the furnace gases to the drying chamber, thls arrangement being preferred where it is found desirable to control the gases entering the drying chamber. In each case, however, the dampery or valve f is adjusted to admit the desired proportion of air to the furnace gases, as hereinbeforel explained, and the damper h or la. is operated to control the total volume of gases passing'through the drier. These vadjustments necessarily are made with reference to the proportion.

of moisture in the fuel and also the nature of the latter in respect to the temperature at which it loses Iits hydro-carbon vapors, as will be understood.

What I claim is: 4

The method of Ipreparing and burning fuel, which comprises feeding the fuel to a. drier, passing the products of combustion from the furnace in which burning is effected through said drier, admixing air with the products of combustion in quantities suflcient to reduce the temperature of the llatter below the combustion point of the fuel plrior to the admlssion of said products to t e drier, separating the dryin medium from the fuel, pulverizlng the fue and feeding the dried and pulverized fuel tothe furnace.

In testimony whereof, I name to this specification.

WILFRED RoTHERY Woon.

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