US2770450A - Method and apparatus for burning cement - Google Patents

Description

Nw., 13, 1956 E. SZINGER METHOD AND APPARATUS FCR BURNING CEMENT 2 Sheets-Shee l Filed June 4, 1953 Attorney Mmm 13, 1956 E. SZINGER 2,770,450

METHOD AND APPARATUS FOR BURNING CEMENT Filed June 4, 1955 2 Sheets-Sheet 2 QQLM-R`QMM By Homey by blowers 37, 38 and 39.

Vlast section ofthe plant and is led to the blowers through charge each container with exactly the same amount of nodules, nor to charge exactly the same amount in each position, but the amount charged into the container in each position should be only so much as will keep the'fire always covered with a thin layer of fresh nodules. Any material carried by the belt past'the container 10 `falls d own a duct 47 and Vis returned by a conveyor 46to the raw material mixing plant.

From the air chambers 23, 24 and 25 pre-heatedpair is forced through the grate openings in the bases of the containers, and flows first vthrough the -clinker layer, which was highly heated in the ignition stage, and completes the burning of any ignition fuel not burnt in the ignition stage. The air then serves for the combustion of the fuel added in the nodules with the raw material. The exhaust gases leaving the containers are discharged to the atmosphere through the hoods 30, 31, 32 and chimneys 49, 50 and 51. By the time the container reaches position 10 it should be full to the top and the burning is nearly complete.A As the height of the material column in the containers increases from position 2 onward,V the air resistance also increases. This fact is taken into account by making the air pressure in the air chamber 24 greater than than that in the chamber 23, and the pressure in the chamber 25 greater than that in the chamber 24. For instance, with a useful height of 4 feet for the container, the pressure in the chamber 23 may be from 2 to 4 inches water gauge, in the chamber 24 from 4 to 6 inches water gauge and in the chamber 25 from 6 to 9 inches water gauge. To enable these different pressures to be produced, the chambers are independently fed with hot air This hot air is taken from the a hood 34 and pipe 53. Dust separators 43, 44, 45 are fixed in front of the blowers to protect them. The dust separated is returned to the raw material mixing plant by the conveyor 46.

No more material is added to lthe containers in positions 11, 12, 13, but the burning proceeds to completion in these positions. The containers are supplied with cold air in these positions by a blower 40 through an air chamber 26, and the exhaust gases pass into a hood 33 and chimney 52, but as their temperature is very high they may, if desired, be used for various purposes, e. g. drying the raw materials.

l Although cooling begins in positions 11 to 13, the main part of the cooling takes place in positions 14 to 19. Since the container leaves position 13 completely burnt, no combustion gases escape in positions 14 to 19. Cold air fed to the containers by blowers 41 and 42 through air chambers 27 and 28 passes through the hot contents and cools them and is thereby pre-heated to a high temperature. This is the hot air which is taken to positions 2 to 10. In order to protect the blowers 37 to 39 from too high a temperature an automatic mixing valve 54 isV xed to the pipe 53 for the purpose of adding cold air to the hot air stream if a given maximum temperature is exceeded.

The container leaves position 19 in a cold condition and in position 20 its contents are discharged. This may be done, for example, by pushing each container into a rotary tipper which inverts each container and subsequently restores it to its initial position. The contents of the container Vare tipped to a coarse sieve 68 through a chute 67. The tipping takes place within a' casing 78, which is connected 'to a dust collector not shown. The large-sized materialV is properly burnt clinker and is separated on this sieve from the line-sized, which contains insufficiently Vburnt material. The large-sized clinker goes from the The invention 'is not limited to the method described or the plant shown. In particular fuel may be saved by charging in position 10 raw cement material without any fuel in a layer of thickness from one-half an inch to three inches. The excess heat from the layers underneath serves to burn this thin layer. i Y n Y Again, instead of supplyinga constant mixture of raw material and fuel to the containers in positions 2 to 9, or 2 to 10 as the ,case may be, two or more separately prepared mixtures may be charged, e. g. on separate conveyors, these mixtures being such that a greater proportion of fuel to raw material is fed to the containers in, say, positions 2 to 5, than in positions 6 to 9.

Although in the plant illustrated, the hot air drawnfrom the containers in the cooling positions is all taken to positions 2 to 10, some of it may be used'for drying cement raw slurry. Alternatively or in addition the hot gases of combustion escaping through the hod 33 may be used for the same purpose. Any of these hot gases may also be employed Vto generate steam, the steam generatorl preferably being placed above the containers 11 to 19. When the heat in the gases is utilised in any of these ways additional solid fuel may be charged as a top layer onto the bed in one or more of the positions 11 to 13 so that by its combustion it heats the gases. Such fuel may also be charged as a top layer into each container in one or more of the burning positions for the same purpose of increasing the available heat in the wastegases.

The plant may be varied by substantiallyvarying the number of positions or the general lay-out or both. For instance, the plant may include two parallel tracks on each of which the containers form an uninterrupted row, each container being moved in turn from one track to the other by means of a traversing platform or like device. In this case the containers on the one track may be in the filling and burning positions and on the other one in the cooling positions, but of course various arrangements are possible.

The containers may also run on a circular track and thenare preferably connected to each other to form an uninterrupted ring. Since in this case complete inversion of each container for the purpose of discharging its contents would be diilicult, the bottoms of the containers may be hinged Vand the discharge effected by allowing each hinged bottom to rock downwards.

Yet again, other cooling systems than the one illustrated may bev 'employedl and the means for discharging Vthe containers continuously or intermittently may be mixtures of raw material and fuel as the burning pro-V ceeds, so that the depthof the bed increases as the burning proceeds from the bottom upwards and the combustion zone during the greater part of the burning is always covered by a thin layer of fresh raw material and fuel, the burnt beds of clinker' being successively discharged so that cement is produced substantially continuously.

` 2. A method according to claim l in which the burning is started by igniting a thin layer of fuel or a mixture of fuel and cement raw material with the aid of a down` draught. v

3. A method according to claim 1 in which the bulk of the charge isfadded continuously to each container` as the burning zone progresses upwards at a'rat'e such that the burning is nearly completeby the tirneuthe containerv is full.

4.7A method according to ,claim 1 in which the pressure of the air for combustion supplied to each container is increased as the burning proceeds from the bottom to the top.

5. A method according to claim l in which the air furnished for combustion has been preheated, the p1e heating being etected by drawing the air through the hot contents of other containers in which the burning is complete so that these other containers are simultaneously cooled.

6. A method according to claim 1 in which the proportion of fuel in the granulated mixture decreases from the bottom to the top of each container as the burning proceeds.

7. A method according to claim 6 in which the last part of the raw cement material is fed to each container Without any fuel.

8. A method of burning cement which comprises the steps of forming a granulated mixture of raw cement material and solid fuel into a bed on the grate of a container; igniting the mixture; supplying air for combustion from below so that the air flows upwardly through the bed; supplying the container from above with additional mixture of raw cement material and fuel as the burning proceeds, so that the depth of the bed increases as the burning in the container proceeds from the bottom upwardly, the combustion Zone during the greater part of the burning always being covered by a thin layer of additional mixture.

9. A method of burning cement which comprises the steps of employing a number of independent containers in which burning takes place simultaneously but in which the operating cycles are staggered; forming a granulated mixture of raw cement material and solid fuel into a bed on the grate of each container; igniting the mixture; supplying air for combustion from below so that the air llows upwardly through the bed in each container; supplying each container from above with additional mixture of raw cement material and fuel as the burning proceeds,

so that the depth of the bed increases as the burning in each container proceeds from the bottom upwardly, the combustion zone in each container during the greater part of the burning always being covered by a thin layer of additional mixture.

10. A method according to claim 8 in which the mixture of raw material and fuel fed to the containers also contains pre-burnt clinkers of small size, the proportion of pre-burnt clinker in the mixture being decreased as the burning proceeds in each container.

ll. A plant for burning cement comprising, a number of sintering containers arranged to move through a defined path in continuous fashion, and in which containers burning takes place simultaneously but with the operating cycles staggered, means for causing; air to flow upwards through each container during the burning, and means for periodically charging raw material and fuel into each container during that part of the cycle in which the burning is taking place so that the depth of the bed in each container increases as the burning proceeds from the bottom upwards.

12. A plant according to claim 1l in which the containers lie beneath :fixed hoods in the burning position and the charging of the bulk of the material is effected through the hoods.

13. A plant according to claim 1l in which the containers enter cooling positions and in both the burning and cooling positions lie above xed air chambers.

References Cited in the le of this patent UNITED STATES PATENTS 1,687,563 Honigmann et al. Oct. 16, 1928 2,090,868 Hyde Aug. 24, 1937 2,646,980 Leftwich July 28, 1953 2,654,588 Somogyi Oct. 6, 1953

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