US2967495A

US2967495A - Method and apparatus for combustion

Info

Publication number: US2967495A
Application number: US762531A
Authority: US
Inventors: Haan Simon De
Original assignee: Shell Oil Co
Current assignee: Shell USA Inc
Priority date: 1957-10-31
Filing date: 1958-09-22
Publication date: 1961-01-10
Anticipated expiration: 1978-01-10

Description

Jan. l0, 1961 s. DE HAAN 2,967,495

METHOD AND APPARATUS FOR COMBUSTION Filed Sept. 22, 1958 2 Sheets-Sheet l INVENTOR:

SIMON DE HAAN Hls ATTORNEY Jan. l0, 1961 s. DE HAAN METHOD AND APPARATUS FOR COMBUSTION 2 Sheets-Sheet 2 Filed sept. 22. 195s FIG.1I

INVENTORI SIMON DE HAAN HIS vATTORNEY BYZ l-United States Patent() lMETHOD AND APPARATUS FOR COMBUSTION Simon de Haan, Delft, Netherlands, assignor to Shell Oil Company, New York, N .Y., a corporation of Delaware Filed Sept. 22, 1958, Ser. No. 762,531

Claims priority, application Netherlands Oct. 31, 1957 2 Claims. (Cl. 110-22) The invention relates to a method and an apparatus suitable for burning solid fuel substantially comprising a mixture of soot and oil and shaped into soft pellets or globules. A fuel of this kind generally comprises a mixture of soot and gas oil and optionally a little water and is obtained by intimately mixing soot liberated from chemical processes with amounts of gas oil, diesel oil or other similar hydrocarbon oil.

As an example of a fuel so formed, reference is made to the solid aggregates of soot and oil formed using as starting material the soot in water obtained in removing soot produced in the partial combustion of hydrocarbon with oxygen to form gas mixtures containing hydrogen and carbon monoxide.

The pellets or globules produced in the above manner generally have an average diameter in the range of from approximately 3 to l5 mm.

A fuel of this type may comprise, for example, 35- 80% of gas oil, ifi-60% of soot (carbon), 0-2% of ash and a few percent of water. It is practically impossible to burn this product in a normal furnace hearth.

It is, therefore, an object of this invention to provide a method and apparatus by which combustion of a fuel of the above type may be effected.

The instant invention now provides a method by which the'above-mentioned fuel is completely burnt, as well as an apparatus suitable for performing this method, which -apparatus is of a compact construction and suitable for connecting, for example, to the front of a normal boiler, furnace or the like.

According to the invention the method of burning this fuel is characterized in that the fuel and primary combustion air are continuously brought together in a primary chamber in which the oil is gasified and at least partially burnt, while at the same time the pellets or globules disintegrate into smaller particles, and that the resultant mixture which contains substantially all the soot in the fuel, is led by the gas stream to a second chamber to which secondary combustion air is also supplied, in which second chamber the remainder of the fuel is completely burnt.

The apparatus suitable for carrying out this method is characterized according to the invention by a gasifica-v tion chamber vprovided with a fuel supply device and a supply for primary combustion air, which gasification chamber is in communication with an axially symmetrical combustion chamber which is provided with a tangential supply for secondary combustion air, which combus- As a result of the gas l ce K 2,967,495

parts; the still unburnt oil vapors then have to burn together with the carbon in the second stage.

In the apparatus according to the invention the narrowed discharge opening for the fiue gases prevents particles, e.g. of the size of a few millimeters, from being entrained after the second stage with the flue gases in an unburnt or -only partially burnt state; the particles remain in the combustion chamber until they are completely burnt.

The gasification chamber is preferably provided, for example, near the bottom, with a grate situated above the primary combustion air inlet, so that this air can only enter the gasification chamber via this grate, which is arranged below the fuel supply device.

The gasification chamber is preferably box-shaped and the combustion chamber is of a cylindrical design with a substantially horizontal center line, both chambers being in communication through an opening in the peripheral wall of the combustion chamber, which opening is narrowed and provided with a lip or tongue which hinders the ow of secondary combustion air to the gasitication chamber.

According tothe invention the combustion chamber may be provided with a circular narrowing which separates the part situated above the gasification chamber from the remainder of the combustion chamber.

The invention will now be described in greater detail with reference to the drawing showing an embodiment of the combustion apparatus according to the invention.v Fig. I is a vertical sectional view of the burner taken on line I--I in Fig. II, and Fig. Il is a vertical sectional view taken on line II-II in Fig. I. Fig. III is a vertical sectional view taken on line III--III of Fig. II.

Referring to the figures, 1 is a box-shaped gasification chamber, while

cylindrical co-axial parts

2 and 3 together constitute the horizontal combustion chamber. The gasification chamber 1 is provided with a fuel supply device 4 and an air inlet 5 for primary combustion air. The secondary combustion air is supplied to the part 2 of the combustion chamber via a tangential air linlet 6; if necessary, further combustion air may also be supplied to the part 3 of the combustion chamber via an air inlet 7,'l The gasification chamber is provided with a grate 8, dis-g posed horizontally and situated between the fuel supply device 4 and the air inlet 5. A feed reservoir 9 is kept constantly filled with pellet-shaped fuel; this reservoir i s funnel-shaped and has steep walls in order to promote', the admission of the fuel to an open vibrating chute 10,` this being desirable in view of the great adhesive power between the particles or globules. Near the gasification,

chamber 1 the vibrating chute 10 discharges into a tube 17 communicating with the gasification chamber 1, aI

shut-off element 18 being arranged between the tube 17.'

and the part of the vibrating chute 10 which is outside this tube, which element has the form of a valve resting on the fuel. The chute 10 is mounted on hangers 20 so that it-is possible for the chute to be brought into vibra" tion relative to the fixed tube 17 by means of thevibra-` ting device 16. Alternatively, the wall of the chute 10 may have a flexible section. Downstream of the valve 18 a supply 11 for compressed air issues into the tubek 17. This compressed air can create an equilibrium ini the tube 17 with the gas pressure in the gasification chamber, so that gas is prevented from leaking'from this chamber via the fuel supply device. fr

It is also possible to use a single or double screw con-l veyor instead of a vibrating chute as supply device for1 the fuel, or a supply chute provided with guide elements.E

The correct selection of the type of supply device which"l it is desired to use of course depends on the type of the fuel; the greater the percentage of gas oil in the fuel pellets, the greater will be the tendency to use a supply Patented Jan. 1o, 196i,

device with moving parts. If the pellets are not too compact, a vibrating chute is greatly to be preferred.

The passage between gasification chamber 1 and the part 2 of the combustion chamber is provided with a lip or tongue 13 which is so shaped and directed that the secondary combustion air which rotates along the `peripheral wall of the combustion chamber while passing the passage is unable to enter the gasification chamber. The combustion chamber which is divided by means of a constricted opening in the two

parts

2 and 3 communicating through a circular opening 14, is also provided with a likewise narrowed opening 15 for the discharge of the combustion gases.

Y Finally, the gasification chamber 1 is also provided with an inspection and ignition opening 12.

The combustion apparatus operates as follows:

The fuel globules are ledfrom the feed reservoir 9 via the vibrating chute 10 and the tube 17 into the gasication chamber 1 where they find their way on to the grate 8. Primary air is led to the gasification chamber via the air inlet 5; this air passes through the grate and the velocity and pressure of this air are such that the fuel pellets, or at least a part thereof, are entrained by the air, in the sense that the pellets dance, as it were, on the grid. The following takes place in the gasification chamber:

(1) Drying and pre-heating of the pellets. v

(2) Evaporation, gasification and partial combustion of the gas oil.

(3) Pulverization and disintegration of the pellets `as a result of the violent movement of the fuel bedlc'aus'cd by the rapid fiow of combustion air through the grate.

Combustion gases enter the combustion chamber via the narrowed opening between gasification chamber 1 and part 2 of the combustion chamber, as well as still unburnt gas oil vapors, which gases and vapors entrain the particles formed in the gasification chamber during the pulverization and disintegration of the pellets. The second ary combustion air which is tangentially supplied via the inlet 6 is mixed with the other media and causes a rotation of the contents of the combustion chamber in the manner known in cyclone burners, so that the solid particles move towards the wall and by colliding therewith disintegrate into still smaller particles. In this part of the combustion chamber the gas oil is further burnt, the carbon is also partly gasified and the particles split up into smaller particles as mentioned above, and in conclusion the cornbustion of the solid particles is initiated.

Complete combustion is finally effected in the la'st part of the combustion chamber of any remaining gas oil vapors and carbon monoxide formed, and finally of the fine particles of solid carbon which enter this part of the combustion chamber under favorable combustionconditions as regards fineness and temperature. On their helical course through the combustion chamber theseparticles have sufiicient time to come into contact4 with air and burn completely. The outlet of the combustion chamber is narrowed to prevent carbon particles near the wall from leaving the chamber unburnt. Thesharp-edged construction 15 promotes the retention of the still unburnt carbon particles. i

It is unnecessary to add air to the combustion chamber through opening 7, if, for example, fuel and combustion air have already been mixed to a sufiicient degree in the two preceding stages. Furthermore, the apparatus can be controlled more readily when the combustion air is supplied in two stages only instead of in three.

Nor is it always necessary to divide the combustion chamber into two parts by means of a constriction, for the combustion will proceed satisfactorily even without such a constriction. Whether or not a constriction of this kind is used depends, among other things, on the composition of the fuel, since if it contains a relatively small percentage of volatile components, the presence of a constriction is an advantage.

In this case the intensity of combustion of the part 2 of the combustion chamber is very high, as both fuel and air are retained for some time and a good mixing takes place. This is accompanied by a high temperature and therefore with much radiation energy which is partially passed to the gasification chamber 1, promoting the ignition of the fuel; ignition ditiiculties in the gasification chamber when the fuel contains a small percentage of volatile components are thus avoided.

If the fuel contains ash with a relatively low melting point, the omission of the constriction will be an advantage, however, because molten ash is thus prevented from finding its way onto the grate 8 through the opening between the part 2 of the combustion chamber and the gasification chamber 1, and the combustion process is not disturbed. Without the presence of a constriction this ash finds its way on to the bottom ofthe part 3 of the combustion chamber, where a draw-ofi' device may or'rn'ay not be arranged. I I

In conclusion it should be noted that the capacityI of ati apparatus as described above is very great, .compared t' known apparatuses for solid fuel, since the grate load this apparatus is approximately 1,200 kg. of fuel per square meter of grate surface per hour.

I claim as my invention:

1. A method of burning carbon particles comprising: mixing carbon particles` with hydrocarbon oil and water to form solid pellets having an average diameter of 3'-15 mm., feeding said pellets continuously into a gasification and partial combustion chamber, introducing air into said chamber, partially burning the pellets with said air in said chamber so that the pellets disintegrate `inl said chamber, passing the resulting stream of gases and disintegrated pellets upwardly into a second chamber of cylindrical shape, introducing a tangential air stream into said secondary chamber whereby further burning of the gases and disintegrated pellets takes placein a horizon; tally axially rotating flame, pattern, thereafter discharging the gases through a narrow axial outlet from said secondary chamber.

2. An apparatus for burning solid fuel pellets containing finely divided carbon and oil comprising: a gasification chamber, a fuel pellet supply means leading into said chamber, a grate in said chamber for supporting fuell pellets in said chamber, a primary air supply means sitilrfl ated below said grate, a first cylindrical combustion chamber having it's longitudinal axis horizontal directly connected to said gasification chamber and mounted thereon, said two chambers being in communication throughan opening in the peripheral wall of said first combustion chamber which opening is narrowedV and provided with a tongue element to hinder the fiow of gases to the gasification chamber from first combustion chamber, a tangentially directly secondary air inlet t'ol said first ccmbustion chamber, a restricted axial outlet piece connecting said first combustion chamber to a second co-axially mounted cylindrical combustion chamber having a tan gentially directed air inlet and a restricted axial outlet piece.

References Cited in the file of this patent` UNITED STATES PATENTS