US2695010A

US2695010A - Furnace for burning solid fuels

Info

Publication number: US2695010A
Application number: US208492A
Authority: US
Inventors: Klijzing Daniel; Idema Katrinus
Original assignee: Directie van de Staatsmijnen in Limburg
Current assignee: Directie van de Staatsmijnen in Limburg
Priority date: 1950-02-02
Filing date: 1951-01-30
Publication date: 1954-11-23
Anticipated expiration: 1971-11-23

Description

Nov. 23, 1954 D. KLIJZING ETAL 2,695,010

FURNACE FOR BURNING SOLID FUELS Filed Jan. 50, 1951 3 sheets-sheet 1 FIG] OOO OOOOOOOOOOOOOOOO INVENTORS DANIEL KLIJZTNG SKATRINUS IDEMA m [3: OM4

ATTORNEYS KLIJZIING ETAL 3,5,m

FURNACE FOR BURNING SOLID FUELS Flled Jan. 1951 Shee'xs-Sheet 2 0 o o o i o 3s; 28

. o l o o o o 3 4 NV E N TOR S V F I G o 4 v I By fill/MAW w fi AT TORNEYS Nov. 23 19% D. KLLJZING ETAL FURNACE FOR BURNING SOLID FUELS s Sheets-Sheet s Filed Jan. 30, 1951 INVENTORS LIJZING DANIEL K KATRINUS DEM/A By a WI! 1:

ATTORNEYS- United States Patent 2,695,010 FURNACE FOR BURNING SOLID FUELS Dani'l Klijzing, Amersfoort, and Katrinus Idema, Voorburg, Netherlands, assignors to De Directie van de Staatsmijnen in Limburg, handelend voor en namens de Staat der Nederlandeu, Heerlen, Netherlands Application January 30, 1951, Serial No. 208,492 Claims priority, application Netherlands February 2, 1950 7 Claims. (Cl. 122-30) This invention relates to a furnace for burning solid fuels, and particularly to those furnaces in which the fuel is introduced at the top into a vertical combustion chamber and primarily combustion air is supplied through apertures in the front wall of the combustion chamber, whereas the gases of combustion are carried off through apertures in the opposite rear wall of said chamber.

In known furnaces of this type the apertured walls are constituted by spaced vertically disposed solid bars, which are liable to be damaged by the fire.

It is the primary object of this invention to prevent damage to the bars constituting the front and rear wall by the heat produced in the combustion chamber.

A further object of the invention is to increase the heated surface and particularly that part of the heated surface which participates in the direct heat transmission in the furnace.

A still further object of the invention is to lessen the tendency of the ashes and fine fuel particles to pass through the apertured walls constituting the front and back of the combustion chamber.

Another object of the invention is to re-introduce particles passed through the apertured walls into the combustion process.

Still another object of the invention is to protect the fuel in the combustion zone against the excessive cooling action of the heat transfer medium.

Further objects and advantages of the invention will become apparent from the following description and claims, and from the accompanying drawings, wherein:

Figure l is a longitudinal section of a furnace installation which can be used in connection with a central heating boiler;

Figure 2 is a cross sectional view of the furnace taken on the line 11-11 of Figure 1;

Figure 3 is a top plan view of the furnace shown in Figure l, in which the feed bin is omitted;

Figure 4 is a sectional view of the furnace taken on the line IV-IV of Figure 2;

Figure 5 is a cross sectional view of the tubes constituting the front wall of the combustion chamber on a larger scale;

Figure 6 is a cross sectional view of the tubes constituting the rear wall of the combustion chamber on a larger scale;

Figure 7 is a front elevation of the tubes shown in Figure 6;

Figure 8 is a side elevation of the tubes shown 1n Figure 6;

Figure 9 is a cross sectional view of the modified construction of the tubes of the rear Wall; and

Figure 10 is a side elevation of the modification shown in Figure 9.

The fuel, for instance large coke, is-stored in a feed bin 1, which is provided with a water jacket 2 and may be closed by a cover plate 3. The bin 1 discharges by means of opening 4 into the top end of the combustion chamber 5, in which the fuel descends by gravity during operation of the furnace.

The combustion chamber is located between the side walls 6 and 7 of the furnace, which side walls are provided with water jackets 8 and 9, and two rows of

watercooled tubes

10 and 11. These tubes terminate with their upper ends in the upper wall 12 of the furnace, which wall is provided with a water jacket 13 communieating with the water jackets 8 and 9 of the side walls. The tubes 10 terminate with their lower ends in the collecting header 14, which also communicateswith the water jackets 8 and 9. The tubes 11 terminate with their 2,595,010 Patented Nov. 23, 1954 lower ends in a collecting header 15 constituting the bottom of the smoke box 16 and communicating with the water jackets 8 and 9. The tubes 10 constituting the front wall of the combustion chamber are disposed with their lower ends at a level higher than the lower ends of the tubes 11 constituting the rear wall of the combustion chamber. By the term tubes" as used in the present specification hollow bars of any cross sectional area are included.

The bottom of the combustion chamber 5 consists of a slightly inclined grate 17, which is composed of a plurality of hollow water-cooled bar-like members, opening in

headers

18 and 19, which headers communicate with the water jackets 8 and 9. A slag pusher 20 is provided, which may be reciprocated or moved over the grate 17 so as to remove the slag underneath the collecting header 14 onto the front portion 21 of the grate. This front portion of the grate permits the slag removed from the bottom of the combustion chamber to be cooled by part of the primary combustion air which is directed over the hot slag so as to be preheated before entering the combustion chamber. In addition, any fuel which may be present in the slag on the extended portion of the grate is given an opportunity to react with the combustion air to effect complete burning of the fuel. By this arrangement a final combustion zone is provided.

The slag pusher is guided with its extension 22 along the slide plates 23 fixed to the header 15, and is provided with two racks 24, cooperating with pinions 25 fixed to the shaft 26, which shaft protrudes outside the furnace. By rotating this shaft the slag pusher may be moved over the grate.

The combustion air is introduced into an air distribution box 27 by means of a thermostatically controlled fan (not shown) connected with its discharge pipe to the inlet openings 28. From the distribution box which adjoins the tubes 10, air passes through the interstices between these tubes and travels in a substantially horizontal direction through the fuel in the combustion cham- The inclined bottom 29 of the distribution box 27 is provided with an opening 30 through which a part of the primary combustion air flows into the area of ashpit 31. Slide plates 32 are adapted to move in the guides 33, which are fixed to the bottom 29 of the distribution box. In this way the size of the air passage 30 can be adjusted. From the ashpit the combustion air flows in a generally diagonal direction through the combustion residue and the overlying fuel disposed on the grate 17.-

The bottom of the ashpit is formed by a base plate 34, whereas the side walls are formed by the walls 6 and 7 and the rear wall 35. Doors 36 are provided to give access to the ashpit in order to remove slag and ashes from the grate 21 and the ashpit.

The ratio between the amounts of primary combustion air entering the combustion chamber through the interstices between the tubes 10 and from the ashpit 31 may be controlled by adjusting either the size of the opening 30 by means of the slide plates 32 or by means of an adjustable passage element 37, which has been disposed in the distribution box in front of the tubes 10. This passage element consists of two sets of perforated plates which are slidably arranged as described in our copending application Serial No. 204,194, filed January 3, 1951. In this way the effective passage area can be altered without disturbing the uniform flow distribution of the air stream passing between the tubes 10 into the combustion chamber by changing the position of the plates with respect to each other.

The combustion gases leave the combustion chamber through the interstices between the pipes 11, from where they-enter the smoke box 16. The conduits 38 connect the air distribution box with the smoke box. These conduits communicate with a tube 3.9 disposed in the smoke box, which tube is provided with a multiplicity of small The amount of secondary air and also the ratio be tween the amounts'of primary and secondary air maybe regulated by means of the control valves 41. From the smoke box the combustion gases flow towards a boiler through a duct 42.

The water. to be heated is introduced into the water jacketsof the furnace; through the inlet 43, whereas hot water or steam leaves thejackets through the outlet 44;. From here it may be sent to the infeed of theboiler or itmay be used for other purposes. The water. jackets. may be emptied through a'tap-otfvalve45;

In operation the fuel descends gradually by gravity from the bin 1 into the combustion chamber 5. As a result of. the horizontally directed and the additional obliquely directed primary air streams, a main combustion zone is developed on the slag. bed S, the form of which resembles that of the region which in Figure 1 has been designated by the reference symbol C. The term main: combustion Zone as used inthe present specification refers to the region where thefuel is substantially burned yielding ashes and partially consumed slag.

As the tubes are cooled by the water flowing. through them, these tubes are protected against. deterioration caused by the h'eatproduced in; the combustion zone. Inorder to; avoid undue cooling. of the combustion: zone adjoining the cooled tubes, which cooling would unfavor-- ably affect the combustion and the formation. of atporous. easily removable slag, the sides of the tubes 10 facing: the combustion chamber are coated with: a refractoryheat-insulating lining 46. In the same way the gratebars 17 are protected by linings 47.

The lower ends 48 of the tubes 10 are turned away from the combustion chamber, the. turned ends opening. into the collecting header 14 at the side facing the combustion chamber and forming. a bottom grid. Ash and fuel particles which have fallen into the air distribution: box- 27 through the slots between the tubes drop through said grid onto the slag bed so that the unburned fuel: particles are re-introduced into the combustion process. Between the tubes 11 a spaced series of fins 49 are disposed al'ong. the tubes. These fins slope downwards towards the combustion chamber. They obstruct the passage of ash and fuel tending to fall into. the smoke box 16 through the slots between the tubes. I

In order to obtain a proper welding joint, the fins 49 are first preferably welded in an oblique position to discs 50,- which on one: side are shaped to follow the contour of the tubes 11. The discs 50 are, in turn, welded or otherwise secured to the tubes 11.

The vertical distance between the projecting elements 49 arranged on one tube may be greater than the average size of the fuel to be burned because, owing to their irregular shape,- the fuel pieces will, in general, be held back even by a few such elements 49 so spaced between the tubes. The arrangement as shown will be sufficient to prevent fuel from falling out of the combustion chamher.- This holds particularly for those cases where large coke is used as a fuel. Care should be taken, however, to leave a space 51 between the projecting elements 49 on two adjoining tubes in order to prevent cracking of the welds owing to expansion of the material during operation of the furnace.

Instead of fins the projecting elements may consist of short rods 52 of a round or rectangular cross section which are welded to the tubes in spaced relation, as shown in Figures 9 and 10.

The CO2 produced in the main combustion zone passes through the incandescent fuel present between the combustion zone and the tubes 11. In this region, indicated in Figure 1 by the reference mark R, the CO2 gas is partly or completely reduced to CO. Subsequently, this gas passes between the tubes 11 into the smoke box where it is mixed with the secondary air admitted through the apertures 40, so that the CO is oxidized to CO2.

We claim:

1. A furnace for burning solid fuels comprising a substantially vertical combustion chamber having a main combustion zone and a final combustion zone beneath and to the front of said main combustion zone, said vertical combustion chamber being enclosed by two side walls provided with water jackets and spaced vertical tubes constituting front and rear walls, collecting headers communicating with said spaced vertical tubes of the front and rear walls and opening into the water jackets in said side walls, means for delivering fuel to said main combustion zone, means for introducing primary com bust-ion airhorizontally through the interstices between tion zone to the final combustion zone to allow complete consumption of the: fuel.

2. A furnace as claimed in claim 1 in which the tubes constituting. said front wall are coated with a layer of refractory material.v

3. A furnace. as. claimed in. claim 1, in which bafiles are. arranged in. spaced: relation between the interstices ofv the tubes constituting said: rear wall so as to obstruct the passage of ash and unconsumed fuel from the vertical combustion chamber to the discharge duct, each of said bafiies is secured to said tubes by a closed welded joint whereby the tubes are less sensitive to cracking caused by a difference in expansion between the tubes and the batfies.

4. A furnace as claimed in claim 3, in which said baffle elements. comprise short rods secured to said tubes.

5. A- furnace asclairned in claim 3, in which said bafile elements comprise obliquely secured fins having their lower edges directedtowards said combustion chamber.

6. A furnace as claimed in claim 5, in which said fins are secured in an oblique position to the faces of discs which are shaped to the curvature of the tubes and are secured thereto.

7. A furnace for burning; solid fuels comprising a substantially vertical combustion chamber having a main combustion zone and a final combustion zone beneath and to the front of said main combustion zone, said vertical combustion chamber behig enclosed by two side walls provided with water jackets and spaced vertical tubes constituting front and rear walls, collecting headers communicating with said spaced vertical tubes of the front and rear walls and opening into the water jackets in said side walls, means for delivering fuel to said main combustion zone, means for introducing primary combustion air horizontally through the interstices between the tubes constituting said front wall into said main combustion zone, a duct for receiving and discharging the combustion gases carried off through the interstices between the tubes constituting said rear wall, said spaced vertical tubes constituting the front wall having their lower ends turned away from said vertical combustion chamber to provide a bottom grid whereby unconsumed products of combustion, which filter through said front wall, are returned to said final combustion zone to be completely burned, said spaced vertical tubes constituting the rear wall having bafiles mounted thereon between the interstices of the tubes and in spaced relationship with each other, said baffles obstructing the passage of ash and unconsumed fuel from the vertical combustion chamber to the discharge duct, a grate beneath said main combustion zone and having a portion extending beyond said zone to a point below said final combustion zone, and reciprocating means for moving the ashes and cinders from beneath said main combustion zone to the final conitbustion zone to allow complete consumption of the fue References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 214,906 Greene Apr. 29, 1879 1,146,743 Thompson July 13, 1915 1,283,668 Cherry Nov. 5, 1918 1,643,026 Molby Sept. 20, 192. 2,504,508 Edling Apr. 18, 1950 FOREIGN PATENTS Number Country Date 2,032 Austria Aug. 25, 1900 763,733 France Feb. 19, 1934 503,172 Great Britain Apr. 3, 1939