US2340431A - Boiler - Google Patents

Description

Patented Feb. 1 19 44 QQSSQES UNITED STATES PATENT OFFICE' BOILER Leonard- Satchwell, Slough, England Application October 29, 1942, Serial No. 463,735

7 Claims. (Cl. 12230) This invention relates to boilers for burning solid fuel under natural draught conditions of the kind in which there is provided Within the boiler a fuel storage hopper or magazine from which the fuel gravitates to the lower part of the boiler where combustion takes place, the gravitation of the fuel being regulated by the rate of combustion of said fuel.

Boilers, where provided and used for natural draught conditions, usually have a firegrate with several small air orifices on which the fuel is burned, the dimensions of such orifices being chosen with regard to the size of the pieces of fuel ordinarily consumed. Difficulty is experienced with such arrangements because of the readiness with which the air orifices become clogged by the ash and many arrangements have been adopted for moving or shaking said grates by manual or other means so as to keep the air passages sufficiently clear to allow a reasonable rate of com bustion to be maintained.

The difficulties referred to above have proved so great in practice that it is now common for such broilers to be supplied with the air necessary for combustion from some pressure source, in an endeavor to maintain the combustion rate.

It has been proposed to avoid these difliculties by providing a boiler in which the fuel is burnt in the form of a pile without a grate under natural draught conditions, and the present invention has for an object to provide an improved form of such boiler. A further object is to ensure that a portion of the fuel will be subjected to a faster rate of combustion than the remainder so as to provide a surface sufficiently high in temperature to ensure ignition of the mixture of combustible gases present in the secondary combustion zone even under light loads. A further object is to provide means for control of the sup ply of secondary air to mix with these gases so as to ensure efficient combustion under different conditions.

-In accordance with a principal feature of the present invention a grateless boiler of the type referred to for burning solid fuel under natural draught conditions is provided with a hopper within the boiler having non-symmetrically disposed inclined water wall portions forming an orifice discharging to form a pile of fuel resting on an imperforate water floor and presenting two fuel faces disposed at an angle in the neighborhood of 90". An opening or openings is or are provided beneath one inclined wall of the hopper for the introduction of primary air which, entering at one fuel face and passing laterally through that portion of the fuel pile which rests on the imperforate water floor, supports combustion within the pile of fuel, the combustion being completed by secondary air supplied above the other fuel face.

As fuel is consumed, reduction of the pile permits flow from the hopper orifice.

In accordance with a further feature of the invention one inclined Wall of the hopper is provided adjacent its lower end over a portion of its width with a projecting portion which serves to reduce the thickness of'the pile of fuel adjacent that portion and thus provides a path of less re sistance than that presented by the remainder of the pile to the passage of the primary air therethrough as a consequence of which even under light loads the fuel adjacent this portion is maintained at a sufficiently high temperature to ignite the combustible gases given off in the secondary combustion zone.

In accordance with a still further feature of the invention the supply of secondary air to the boiler is controlled in dependence on the supply of primary air so as to ensure the admission of an amount of secondary air only sufiicient to ensure combustion of all the gases and prevent the cooling of the chimney by the flow of secondary air when the boiler is operating under light loads and the flow of combustible gases from the pile is reduced.

In the accompanying drawings:

Fig. 1 is a sectional elevation of a boiler embodying the invention;

Fig. 2 is a view along line 22 of Fig. 1;

Fig. 3 is a sectional elevation of another embodiment of the invention, and

Fig. 4 is a view along line 44 of Fig. 3.

Referring now to the drawings, the boiler is constituted by inner and outer walls I and 2 providing a water wall 3, the walls I and 2 being braced by means of stays l. 5 indicates the fuel pper one wall of which is spaced from the adjacent wall of the boiler and is constituted by inner and outer walls 6 and l braced by stays 8 defining therebetween a water wall 9. The lower portion II] of this water wall of the hopper is inclined downwardly towards the opposite side of the boiler. In the construction shown in Fig. 1 the opposite wall is constituted by inner and outer walls I and 2 extending from the upper end of the boiler while in the construction shown in Figs. 3 and 4 this upright wall is a water wall for a short distance within the hopper and above that level consists of single plates 6 as do the two other side walls of the hopper indicated clearly in Fig. 4. The arrangement of the water walls shown in Figs. 3 and 4 is preferred and since with this arrangement the surfaces of the hopper other than the wall 6, I spaced from the?,.

of the walls It] and I I ensures that the fire area is appreciably removed from the outlet of the hopper and prevents the fuel from burning. upwards in the hopper. The floor I3 of the boiler is an imperforate water floor and is suitably inclined upwards as indicated at I4 towards a clinker door I5. The spacing of the wall I of the hopper from the outer water wall 3 and the inclination of the lower portion of the wall It provide a secondary combustion zone it with a secondary air inlet manifold 2i anda passage I'I forthe flow of combustion gases upwards to a flue I8 disposed at the top of the boiler. The exit of the hopper may be controlled or closed by any suitable device. For example, a sliding'damper or 'thelike may be provided to allow the fuel to ilowwhen the boiler is started up, to regulate the flow'of fuel and to out off the supply of fuel before declinkering or drawing of the boiler fire. The lower portion l I of the one wall is of greater length than the portion It of the other wall and forms as stated above a fuel directing water wall, the surfaces of which are arrangedat an angle to allow free' movement of the fuel. In'one or more walls of the boiler there is provided a large opening to provide for the free'admission of, air to the pile of fuel l9 disposed between the wall I I and the floor it and combustion takes place by the passage of air through the sloping face of the pile of fuel. From the centre of the lower end of the fuel directing wall I I extends a projection 29 which modifies'the cross section or; the central portion of the fuel pile so as to provide a small area through which the length fof travel of the primary air is much less than through the remainder of the fuel pile, thus ensuring a faster rate of combustion in this small area and providing a surface onthe second .fuel face which is always sufficiently high in temperature to ensure ignition of the mixture of the combustible gasespresent in the secondary combustion zone IS. The wall of the boiler vertical to' the floor is inclined or curved as at Ma to meet the floor. The secondary air manifold ZI is connected to the primary air space below the water;

volume of'air for both'primary and secondary combustion. As the demand on the boiler isreduced the thermostat will cause flap 28 gradually to close so reducing the volume of both primary and secondary combustion air. At times, partic V ularly when the demand on the boiler is very small,- flap28 may actually be closed so thatunder such circumstances combustion may be almost suspended and it will be obvious that it is very desirable that the supply of secondary air should also be stopped since otherwise the cool secondary air would merely act to cool the hot surfaces of the boiler, thus greatly reducing the boiler efliciency under such conditions. If desired the control of the secondary air supply may be carried out by the provision of a second flap or valve operated by the thermostat whichrcontrols the position of flap 28 or alternatively by a second thermostat. If desired also, the admission of air through the opening 28- can' be controlled by a valve or flap attached to alever controlled by a thermostat disposed in the hot water space of the boiler.

22 and 23 indicate flow and return connections to the heating system.

i The whole boiler is enclosed in a substantially rectangular casing 24 built up of welded steel plates; The hopper5 is provided with an inlet chute 25 covered by a door 26.

I claim:

1. A grateless boiler for burning solidfuel under natural: draught conditions, said boiler having an imperforate water floor, a plurality of water walls forming the sides of a fuel hopper within said boiler from which fuel gravitates' to sai d floor to form a pile presenting two fuel faces, means for supplying primary air to one of said fuel faces, a secondary combustion space within said sides and above theother of said fuel'fa ces and means for supplying secondary air thereto, means providing a path of limited area and of low resistance to the passage ofpri'mary. air through the pile of fuel, and means for controlling the supply of secondary air in dependence on the supply of. primary air. i K

' 2. A grateless boiler forburning solid fuel un der natural draught conditions comprisingan imperforate water'fl'oona pluralityof water walls forming the sides of a fuel hopper withinthe boiler, said hopper including inclined water-"wall portions, said wall portions being non-symmetrically disposed within the boiler and'providingan rifice discharging thefuel to the floor, to form apile. presenting two fuel faces, means for supplying primary air for combustion beneath one inclined;

wallofthe hopper so asteenter at one fuel face and pass laterally through thefuel pile, means providing a path of limitjed area and of low re sistance to the passage of primary air throughv the'pile,'a secondarycombustion space above the other. fuel face, means for supplying secondary: air theretoto complete the. combustion and: meansicontrolling the supply of secondary air in dependence on the supply of primary air. 1

3; A'boiler as claimed claim 2, in which the. wall portion of they boiler immediately under, the. secondary'combustion space is curveddownwards' to meet the floo'rflf V 4. grateles'siboiler for burning solid fuel under, natural. draft conditions which-comprises an imperforate water floor, a'plurality of water walls,- 7

providing sides for a fuel hopper withinthe boiler, the lower portions o f 'two opposite waterwalls sloping'towards each other one being short and;

thef'other' long with a space between the lower means for supplying air to the secondary comtion of the long sloping water wall through which the fuel is free to fall from the secondary combustion space and accumulate on the water floor, means for supplying primary combustion air to burn the fuel accumulated on the water floor, and means providing a path of limited area and low resistance for the passage of combustion gases from the fuel burning on the water floor to the presenting two fuel faces, means for supplying primary air to one of said fuel faces, a secondary combustion space above the other of said fuel faces and means for supplying secondary air thereto, and means for reducing the cross-section of the fuel pile between the fuel faces.

7. A grateless boiler for burning solid fuel under natural draught conditions comprising an imperforate water floor, a fuel hopper Within the boiler, said hopper including inclined water wall portions, said wall portions being non-symmetrically disposed within the boiler and providing an orifice for discharging the fuelto the floor to form a pile presenting two fuel faces, means for supplying primary air for combustion beneath one inclined wall of the hopper so as to enter at one fuel face and pass laterally through the fuel pile, means for reducing the cross-section of the fuel pile between the fuel faces, a secondary combustion space above the other fuel face, and means for supplying secondary air thereto to complete the combustion. Y

LEONARD SATCHWELL.

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