US2894466A - Solid fuel flow controller - Google Patents

Description

July 14, 1959 R. M. L. MARTIN soLID FUEL FLow coN'rRoLLER 'Filed DecQ v1, 1953 W W W United States Patent O The present nvention has for its object improvements relating to burners and furnaces which utilise solid fuels. As a general rule, in this type of apparatus, the fuel .which is held inreserve vis contained in a hopper from which it passes into the furnace, either under the simple effect of gravity, or after having passed through a mechanical member which regulates the quantity passed through, and which is commonly known as the fueldistributor.

This distributor regulates the quantity of fuel which is introduced at each instant into the furnace. This quantity of fuel introduced should, in practice, be approximately equal at every instant to the quantity of fuel consumed at the same instant, if it is desired to obtain stable conditions of combustion or gasification.

The ,nvention has a special interest in the case in which the furnace operates in accordance with the multi-stage process of'combustion as described in the specification of British Patent No. 669,914, in which the fuel moves successively through a distillation zone, a combustion and gasification zone and a zone of combustion of unburnt= solid matter mixed with the cinders and clinker, and in which a fraction of the air is injected into the furnace from a point close to the arrival of the fuel.

The present nvention solves this problem in a very satisfactory way and to that end provides a furnace of the kind referred to, supplied with solid fuel from a hopper via a conduit, wherein the quantity of fuel undergoing combustion and the air supplied are retained approximately constant by means of a movable flap suspended inside said conduit and actuated in dependence upon the variations, within the opening of said conduit into the furnace proper, of the level of the summit of the heap of fuel resting on said grate, said conduit housing a fuel distributor Controlled by said flap and being formed with an air injection orifice, whereby not only the level of the summit of the fuel, but also the crosssection of the air passage remaining between said summit and said conduit opening, is retained approximately constant.

Other characteristics and advantages of the present nvention will become clear from the description which follows below, and which is made in respect of the attached drawing, the single figure of which shows, in longitudinal cross-section, in diagrarnmatic form and solely by way of example, one possible form of embodiment of the nvention.

The apparatus shown includes, in accordance with usual practice, a hopper 1 containing the reserve of fuel, a conduit 2 connecting this hopper to the furnace proper 3, and a distributor 4, which controls the quantity of fuel passing into the furnace.

The apparatus comprises in addition a grid or blastorifice 5, by means of which the air is distributed under the fuel and under which there is arranged an air-intake opening 6. The gases generated in this apparatus escape through a gas-Outlet conduit 7. i

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In accordance with the nvention, a feeler device 8, constituted by a mobile shutter fixedly mounted on an axis 9, is suspended inside the conduit 2 below the fuel distributor 4. The axis 9 is connected to the control means of the distributor 4.

The to and fro movement of'the feeler device 8 caused by variations in the upper level of the layer of fuel passed into the apparatus is'communicated by this means to the control of the fuel distributor.

The fuel is shown in the apparatus in the form of a pile or heap 10, the summit 11 of which emerges under or inside the conduit 2 at the level of the feeler device 8. The differences which may arise between the quantity of fuel supplied and the consumption of this fuel always show themselves finally in the form of a displacement of the summit 11 of the heap in course of combustion or gasification.

The apparatus provided with improvements in accordance with the nvention operates in the following manner:

When the summit 11 of the layer of fuel or of the heap 10 rises to a greater or less extent under the effect of an arrival of fuel, this summit 11, as it rises, pushes away the shutter of the feeler device 8. This shutter is pushed aside from its position of equilibrium by an amount which increases as the summit of the layer of fuel rises.

In consequence of the movement of the shutter, the shaft 9 turns on its axis and acts on 'the control of the motor 13 of the distributor 4.

The level of the summit 11 of the layer' of fuel is permanently maintained at a value which is approximately constant.

It may be said that the apparatus in accordance with the. nvention, together with its feeler device, behaves in an analogous manner to the Constant level chamber of 'a lcarburetor of an automobile. The control of the distributor motor 13 may be constituted, for example, by a switch 14 (mercury switch, etc), which effects the starting up or the stopping of the motor, in accordance with the level of the summit of the layer of fuel.

This control may equally well be made up of a device by means of which the output of the distributor may be varied, which will give a progressive regulation instead of the full-on or fully-off regulation given by the switch.

There may, for example, be applied the idea of a control lever operating a field rheostat fixed to the shaft 9, the lever moving along different studs of the rheostat and thereby varying the field current of the stator of a direct current motor supplied with a constant voltage.

The sensitivity of the control is, in this case, only conditioned by the sensitivity of the movement of the shutter and of the connecting member.

The nvention has quite a special interest in the case in which the furnace operates in accordance with the process of combustion known as the multi-cycle process, and in which a fraction of the air is injected into the furnace from a point close to the arrival of the fuel.

In this case, the air in question, which is introduced through an orifice 12, and the fuel both pass into the furnace through the same conduit 2. Any Variation in the height of the summit 11 of the layer of fuel leads to a Variation in the cross-section of passage of the air at this point and, in consequence, to a Variation in the rate at which it is supplied.

The feeler device 8 in aceordance with the nvention, thus enables the passage cross-section to be controlled and therefore the quantity of air injected through the same conduit as the fuel, thereby making stable the conditions of combustion.

In a general way, the above description is only given by way of indication and not in any limiting Sense, and the invention is capable of numerous variations in accordance with its spirit.

I clairn:

1. A furnace having a fuel distributor, a hopper, a conduit having -an inlet communcating with said distributor and an outlet therebelow, means including a grate to which fuel is fed from said hopper 'via said conduit supporting said fuel in a heap with the top Vthereof in alignment with the outletof said conduit and in outlet cross-section diminishing relationship therewith, and operated according to a multi-stage system of combustion as herein set forth, wherein a movable .fiap suspended inside said conduit land actuated in dependence upon the variations of the size of the heap of fuel resting on said grate, retains approximately Constant the quantity of fuel undergoing combustion andat least some of the air supplied, said conduit housing said fuel distributor Controlled by said fiap and being formed with an air injection orifice, whereby not only the level of the summit of the fuel, but also 'the VCross-section of the air passage remaining between said Summit and said conduit opening, is retained approximately Constant.

2. In a furnace, a hopper, a motor driven fuel distributor at the delivery end of said hopper, a conduit below the discharge end of said distributor and having yits upper intake end Communicating with the discharge end of said distributor, a combustion Chamber, the lower end of said conduit connected with said combustion Chamber to conduct fuel thereto from said distributor, said Vcombustion Chamber having means therein to support fuel in a heap with the top of the heap being in alignment with the lower end of said conduit and variable between positions in 'the vicinity of the lower end of said conduit, means to sense the position of the top of the fuel in said combustion Chamber, said means being Connected with said motor to control the operation thereof to start the motor when the top of the fuel is in .a low position and to stop the motor when the top of the `fuel is in a higher position, said conduit .having air introduction means therein, whereby the Control of the position of the top of the fuel heap also controls the air passage soi into said combustion Chamber from said air introduction means.

3. A furnace having an auxiliary hopper -for fresh fuel, a motor-driven fuel distributor communicating with the hopper and having an outlet, a combustion Chamber having an inlet adjacent its top and Comprising means for supporting the ignited fuel as a heap, a substantially Vertical conduit connecting the distributor outlet to the combustion Chamber inlet, through 'which the fresh fuel falls directly into the furnace from the outlet of 'the distributor, and into which Communicates an air inlet for introducing into the conduit a fractiontof the combustion air, means in said furnace for sensing the position of the upper surface of the heap of ignited fuel, said means being operatively connected to said -motor to start it when the upper surface of the fuel heap is below a predetermined position and to stop it when the upper surface of the fuel heap is above a predeterrnined position, both these positions being close to each other, so that the amount of ignited 'fuel in the hearth .is maintained substantially Constant, the amount of fresh fuel introduced for va given period being substantially equal to the amount :burnt during .that same period, while the fraction `of combustion rair introduced into said conduit remains .substantially Constant, whatever the variations of the amount of fuel burnt during =a given period and of the total amount of combustion air introduced during the last said period.

References Cited in the file of this patent vUNITED lSTATES PATENTS `l1,00(),038 'Reck Aug. 8, '1911 V1`,263;035 Casler Apr. 16, 1918 '1,3l2,352 Pinet et al. Aug. 5, 1919 1,36'6,434 i Thomson Jan. 25, 1921 V1,511,279 Jackson Oct. 14, 1924 1,641,545 McCoy Sept. 6, 192.7 -1,958,095 Papez May 8, 1934 2,131,305 Shaw Sept. 27, 1938 2,466,170 Harrington Apr. 5, 1949

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