US2569639A - Furnace grate bar - Google Patents

Description

Oct. 2, 1951 R. M. L. MARTIN 2,569,639

FURNACE CRATE BAR Filed 001:. 31, 1945 2 Sheets-Sheet 1 I, a H H H R Oct. 2, 1951 R. M. L. MARTIN FURNACE CRATE BAR Filed Oct. 51, 1945 2 Sheets-Sheet 2 Patented Oct. 2, 1951 FURNACE GRATE BAR Roger Marie Leonce I Application Solid fuels contain water, mineral substances called ashes, and a combustible part. Under the action of heat sheltered from the air, this latter part disintegrates into two parts, one of which comprises gaseous volatile matters, and the other of which comprises coke which generally consists of almost pure carbon.

The volatile matters are set free and will burn when in contact with air. The coke and the ashes remain on the grate. V

In particular the problem of gasifying solid fuels consists first in bringing about the gasification of the carbon contained in the coke and mingled with the ashes, and further in evacuating the ashes in such a manner that no appreciable quantity of carbon is carried along with them.

Therefore it is necessary to obtain a very even distribution of the gasification air under the whole surface of the fuel bed, as well as the quiet and regular passage of this air through the whole mass of fuel.

This result is very diflicult to obtain because the resistance of the mass is irregular in consequence of the difierent sizes of the pieces of fuel and the formation of melted ashes which agglomerate into lumps. sistance is formed in part of the fuel bed, the quantity of air increases in this part of the fuel bed with respect to other parts thereof, and thus the gasification of the fuel and the formation of chokers accelerates at this part. ensues an intensification of those phenomena which leads to undesirable results. This is what occurs in particular with the ordinary grates which consist of bars of triangular section with the triangle pointing downwards and allowing the air for the gasificationto pass between them.

In order to overcome this difl'iculty, numerous devices have been considered for the purpose of increasing the resistance presented by the grate to the passing air.

It is known that for this purpose a grate of thick, closely spaced rectangular bars or a grate consisting of a thick plate provided with cylindrical holes of small diameter may be employed.

increased loss of pressure through the grate When a path of least re- Hence there 7 is obtained by reducing the outlet apertures for Martin, Boulo gne stir-Seine, France October 31, 1945, serial No. 625,841 In France June 27, 1945 6 Claims. (01. 110 .30)

2. For the same total flow of air, the section is smaller and the speed of the air therefore is increased, which fact causes dust to be carried along with the air and does not produce an equal and regular passage of the air through the whole mass of fuel.

-Equal distribution of the air throughout the fuel layer is more difficult to obtain where the fuel contains ashes and. is in small pieces. The more ashes there are, the greater will be the risk of clinkers being formed and of carbon being carried along in the melted ashes. The smaller the pieces of the fuel, the greater is the resistance presented to the passing air and the greater the risk of lack of equilibriumbetween the difierent points of-the fuel bed in gasification or in combustion.

The present invention has for its object to solve these problems and to obtain first a great loss of pressure through the grate, this loss being even larger than that through the layer of fuel, and secondly a large section of passage and a small speed of the air in contact with the fuel, so as to obtain an equal distribution of the air throughout the layer and a regular combustion.

Grates conforming to the invention are represented by way of example in the accompanying drawings, in which:

Figure l is a sectional view of a grate showing the inlet conduits for the air;

Fig. 2 is a plan view of the grate of Fig. 1 as viewed from above;

Figure 3 is a sectional view of another embodiment of a grate constructed in accordance with the invention and showing the inlet conduits for l the air;

Fig. 4 is an elevational view of the grate of Fig. 3 as'viewed from the right hand side thereof Figure 5 is a partial elevational View of a grate formed by several superposed bars;

Figures 6 and 7 show sections through the grate of Fig. 5, respectively taken along the lines 6-6 and 'l-| of Figure 5 and looking in the direction of the arrows; and

Figure 8 represents a vertical sectional view of a gas-producer equipped with a grate according to the invention.

In the grate shown in Figs. 1 and 2 the conduits for the passage of the air consist of two parts, one 5 in shape of a nozzle on the side where the gas enters, and another 6 having the form of an expansion chamber on the outlet side of the gas. In this way there is produced a strong resistance to the passage of air, a large section of passage for the air when contacting the fuel with a small Mi; speed of the air at this place.

lee: 1

It is not feasible to place such a grate horizontally, because the small apertures of the nozzles would be obstructed by the ashes. Therefore it is desirable to place the axes of the nozzles in a substantially horizontal position. In such position the nozzles are not; subject to being obstructed by' the ashes.

Such an arrangement is shown in Figs. 3. and 4. where the direction of air fiow through the nozzles 5 and the expansion chamber 6 is substantially horizontal.

Figures 5 to '7 show a grate 1 consisting of superposed prismatical bars 8 having horizontal supporting surfaces and pierced with horizontal conduits 5" and 6", such arrangement. forming on one side of a nozzle 5" and on the other. side an expansion chamber 6", the bars being provided on the lower side with a notch 9 and on the upper side with a projecting piece I of same height as the. notch. However, the projecting; pieces and notches are of a little lesser height than that of the horizontal air-expansion chambers through which the air is conducted,

into contact with the fuel.

The grate bars are spaced in Figs. tn 7 mereIy: for descriptive purposes. Actually they rest. directly on each other.

With a grate thus constituted by superposed bars, a throttling is produced on the side where the air. enters, and then the conduit section is of increased size up to the side of the grate which is in contact with the fuel, so that the air is at a low speed when it arrives at the fuel.

The bars may be straight, in the form of a crown or of any other shape accordingly to whether it is desired to have a level grate, a circular grate or a grate of a particular form.

The evacuation of the ashes is effected below the grates and may be obtained by means of any known device.

A gas producer equipped with a grate according to the invention is shown, by way of example, in Figure 8.

The apparatus is essentially. constituted. by a grate l according to the invention, a bottom l2 adapted to support the ashes and clinkers dropping from the grate, a rake 13 to which a reciprocating movement is imparted for extraction of the ashes supported by the bottom l2, an outlet [4 for the gas located between the two fuel descents, a special member I5 separating the feed-hopper from the gas-producer and allowing the gases to flow towards the. outlet 14, the tubes [6 through which circulates air for cool!- ing the member I5, which air thus heated may be used for the combustion of the produced gas or as air for gasification, a feed-hopper ll containing the fuel supply, and lastly the shutters l8 separating the hopper from the gas-producer, and placed in the fuel descents IS.

The apparatus to be used maybe of any'other form and may for instance be out along its axis, leaving thus only one slope of descent.

I claim:

1. A flat grate composed of a plurality of parallel arranged grate bars having each a prismatic shape; a continuous projection on the upper face of each said prismatic grate bars arranged along and adjacent the outer face of the same; a continuous notch in the bottom surface of each of said grate bars arranged along and adjacent the outer surface of the'saine and shaped so that the projection of the adjacent grate bar fits into it; a plurality of air passages provided in each 4 of said grate bars in the bottom surface thereof and shaped so as to be higher than said projections on the upper surface of said grate bars immediately below the passages so that the projection of the adjacent grate bar reduces the diameter of each of said air passages near the outersurface of said grate: bar so that each of aid. air pas a e mpose f a relatively row outer portion and a relatively wide inner portion.

2. A flat inclined grate having an outer surface and a fire surface and composed of a plu- I rality of superimposed parallel arranged grate rate and. shaped o hat aid.- pr icot onson sa d; rate bars fitinto said notches in adjacent rate I bars; a plurality of vertically extending parallel horizontal air passages provided in each of said grate bars in the bottom surface thereof and shaped so as to be higher than saidprojections on the upper surface of said grate bars immediately below the passages so that said projections reduce the cross section of each of said air passages near the outer surfaee'of each ofsaid grate bars so that each of said air passages is composed of a relatively narrow outer portion near said. out r sur a f said f t in l ned state.

and a relativ ly wide inner p rtion near said. fire v surface of said flat inclined grate.

3,. A fire gra ha n n o ter ur ce and an.

inner surface on which the fuel to be. burned on said grate is supported, said outer surface being substantially parallel to said inner surface, and

said grate having a plurality of substantially parallel rows. each consisting of a plurality of spaced sv al a r-pa age formed therein and ex: ending from the outer to the. inner surface. of Said ra e. each of said air-passages being com pletely separated and spaced from the other air v 1 passages and having a cross-sectional areas-uh v stantially larger at that portion thereof which is adjacent to said inner surface than the cross- 5 sectional area at that portion thereof which is adjacent to said outer surface, each of said airpassages having a length from said inner surface to said outer surface-which is greater than any transversal dimension of said air-passages parallel to said surfaces of said grate.

4. A fi e grate h a o ter surfa e and an inner surface on which the fuel to be burned on said grate is supported, said outer surface being substantially parallel to said inner surface, and said grate having a plurality of substantially parallel rows each consisting of a plurality of pa ed transversal air-passa es formed therein and extending from the outer to the inner S111: face of said grate, each of said airs assages being completely separated and spaced from the other air-passages and having a cross-sectional area 4 substantially larger at that portion thereof which is adjacent to Said inner surface than the cross-sectional area at that portion thereof whi h is adja ent to said ou surfac h ax s of each of sai a rmassases form n an acute angle with said surfaces, and the length of each of said air-passages from said inner surface to said outer surface being greater than any trans versal dimension of said air-passages parallel to said surfaces of said grate.

5. A fire grate having an outer surface and an inner surface on which the fuel to be burned on said grate is supported, said outer surface being substantially parallel to said inner surface, and said grate having a plurality of substantially parallel rows each consisting of a plurality of spaced transversal air-passages formed therein and extending from the outer to the inner surfaces of said grate, each of said air-passages being completely separated and spaced from the other air-passages and having a cross-sectional area substantially larger at that portion thereof which is adjacent to said inner surface than the cross-sectional area at that portion thereof which is adjacent to said outer surface, said cross-sectional areas at those portions of each of said air-passages which are adjacent to said inner and outer surfaces, res ectively, being substantially uniform, the axis of each of said air-passages forming an acute angle with said surfaces, and the length of each of said air-passages from said inner surface to said outer surface being greater than any transversal dimension of said air-passages parallel to said surfaces of said grate.

6. A fire grate having an outer surface and an inner surface on which the fuel to be burned on said grate is supported, said outer surface being substantially parallel to said inner surface, and

said grate being composed of a plurality of parallel adjacent bars shaped so as to form between themselves rows consisting of a plurality of transversal air-passages extending from the outer to the inner surfaces of said grate, each of said air-passages being completely separated and spaced from the other air-passages and having a cross-sectional area substantially larger at that portion thereof which is adjacent to said inner surface than the cross-sectional area at that portion thereof which is adjacent to said outer surface, said cross-sectional areas at those portions of each of said air-passages which are adjacent to said inner and outer surfaces, respectively, being substantially uniform, the axis of each of said air-passages forming an acute angle with said surfaces, and the length of each of said airpassages from said inner surface to said outer surface being greater than any transversal dimension of said air-passages parallel to said surfaces of said grate.

ROGER MARIE LEONCE MARTIN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 581,347 Greene Apr. 27, 1897 689,827 McClave Dec. 24, 1901 702,538 Campbell June 17, 1902 1,026,645 Bigelow May 14, 1912 1,464,190 Webster Aug. 7, 1923 1,553,587 Balmfirth Sept. 15, 1925 1,769,157 Newkirk July 1, 1930 1,843,000 Rich Jan. 26, 1932 1,895,511 Hulson Jan. 21, 1933 1,989,514 Harlow Jan. 29, 1935 2,070,894 Gorsuch Feb. 16, 1937 FOREIGN PATENTS Number Country Date 18,326 Great Britain Nov. 1, 1890 548,213 France Jan. 10, 1923

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