US2654589A

US2654589A - Construction and operation of vertical shaft furnaces

Info

Publication number: US2654589A
Application number: US127754A
Authority: US
Inventors: Somogyi Francis Paul
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-11-17
Filing date: 1949-11-16
Publication date: 1953-10-06
Anticipated expiration: 1970-10-06

Description

Oct. 6, 1953 F. P. SOMOGYI ,5 I

CONSTRUCTION AND OPERATION OF VERTICAL SHAFT FURNACES Filed NOV. 16, 1949 Patented Oct. 6, 1953 UNITED STATES ATENT OFFICE CONSTRUCTION AND OPERATION OF VERTICAL SHAFT FURNACES Francis Paul Somogyi, London, England 6 Claims.

This invention relates to improvements in or relating to the construction and operation of Vertical shaft furnaces of the kind in which discrete material consisting of or containing a solid fuel is charged from the top and passes down the shaft in countercurrent to an ascending air blast introduced into the bottom, and is finally removed from the bottom of the shaft. As the material passes down the shaft its temperature progressively increases until the material reaches a point at which combustion commences. This point represents the boundary between the heating zone and the combustion zone. As the material passes down through the combustion zone its temperature first rises and then falls until the material reaches a second point at which combustion ceases. Thereafter the material progressively cools until it reaches the bottom of the shaft. The second point represents the boundary between the combustion zone and the cooling zone.

Since heat is lost from the shaft by radiation in a radial direction, the temperature of any given horizontal cross-section of the material is higher at the centre of the shaft than at the circumference. As a result, the depth of the combustion zone is considerably greater at the centre of the shaft than at the circumference.

It is the main object of the present invention to avoid this difficulty; other objects and improvethe kind specified, wherein a part of the ascende ing air blast introduced into the bottom of the shaft is removed at one or more levels from the periphery of the cooling zone, so that a part only of the air blast proceeds onwards up through the combustion zone.

According to this invention also, there is provided a vertical shaft furnace of the kind specified, having means for introducing an ascending air blast into the bottom of the shaft, an outlet or outlets for combustion gases at the topof the shaft, and one or more peripherally disposed outlets at one or more levels, for a part of the blast air from the periphery of the cooling zone of the s aft.

By means of the invention it is possible toin- 2 ing zone reduces the tendency of the combustion zone to extend further down the shaft at the centre than at the circumference, and thus renders the combustion zone more nearly uniform in depth.

The invention may be applied with advantage to cement-making. Since the material, in this case burnt clinker is now discharged from the bottom of the kiln at a lower temperature than Was previously usual, less timeelapses after its discharge before it has cooled sufficiently to be further handled, and this saving of time is of advantage. Moreover since the depth of the combustion zone is more nearly uniform, the conditions experienced by the material passing down the shaft vary less with the radial distance of the material from the centre of the shaft than was previously the case and therefore a more nearly uniform product results. The quicker cooling also improves the quality of the product by freezing in of the calcium silicate.

The blast air removed from the periphery of the cooling zone is at a relatively high temperature, and may be used for one or more of a number of purposes. For example in thecase of cement-making, the blast air from the cooling zone may be passed to a drying device in which it is used to pre-dry nodules or briquettes of cement-forming material before the latter is charged into the kiln.

By controlling the input of blast air into the bottom of the shaft, and the escape of blast air from the cooling zone, the lower boundary of the combustion zone may be adjusted upwards and downwards as desired.

The blast air removed from the cooling zone may be returned wholly or in part into the combustion zone through peripheral inlets, and the proportion of blast air removed from the cooling Zone and the proportionof blast airreturned t'o the combustion zone may be. regulated and controlled so as to adjust the lower boundary, of the combustion zone upwards and downwards. A proportion of the blast air removed from the cooling zone may also, if desired, be returned through peripherally disposed inlets into the heating zone whereby heat from the blast air may be re-introduced into the system.

Control may be effected by a relay mechanism actuated by temperature responsive devices, such as thermo-couples, disposed in the furnace wall at different heights and different sides of the furnace, and the arrangements may be such that the lower boundary of the combustion zone is rotary grate is mounted on a shaft :5 which is connected to driving means not shown. The upper part of the chute 4 is provided with an inlet 6 through which an air blast is introduced into the bottom of the shaft 2.

A feeding hopper 1 having a chute 8 is disposed vertically above the top-of the shaft 2 and enclosed in a housing 9 having a chimney Ill for the outlet of combustion gases. The kiln is charged with .solid fuel andcement-formingmaterial in the form of nodules or briquettes 'I I.

Intermediate the upper and lower ends of the shaftlZ a number of-ou'tle'ts l2, distributed around the periphery and each having a .proportioning valvejl3, lead from the interior of the shaft 2 into manifolds 14 disposed .on either side of the kiln and interconnected at their upper ends to ,form a single escape conduit 15 having a control valvellidisposed in the conduit l5 above the point of interconnection.

Partway down from the top of the shaft a K number of openings 11 communicate with the manifolds l4 and constitute inlets l8 each of which has a propor'tioning valve l9, whereby the manifolds M are placed in communication with the 'interior of the upper part of the shaft 2.

Intermediate the outlets l2 and the inlets It further inlets around the periphery of the furnace lead from the manifolds 14 into the interior of the shaft 2 each of which is provided with a proportioning valve 2 I. Partway 'up from the bottom of the shaft 2 two additional diametfically opposed outlets 22 lead from the interior of the lower part of the shaft into the manifolds M.

The escape conduit 15 communicates with a drying chamber 23 having an outlet 24 into the chimney 1 0. A feeder conveyor 25 passes through the drying chamber 23 from which the material is discharged through a chute 26 into the hopper 1;

Above and adjacent to each of the inlets l8 and 20 and the outlets I2 a thermo-couple 21 is inserted in the wall :of the kiln I. The thermocouples 2] are electrically connected to a regulator 28 which in turn is electrically connected ,toeach of the proportioning valves I3, I9 and 2|. "The electrical connecting means between the "thermo-couples and the regulator, and between the regulator and the proportioning valves are indicated diagrammatically by dotted lines and may be carried out by any known means.

The-cement kiln functions as follows:

Solid fuel and cement-forming material in the 'formiof modules or briquettes ii is charged into the top of the kiln I and passes down the shaft ,2 :in counter-current to an ascending air blast. As the material passes down the shaft its temperature progressively increases until 'the' material reaches a point at which combustion commences. This point represents the boundary between the pre-heating zone A and the combustion zone B. As the material passes down through the combustion zone B its temperature rises and falls until the material reaches a second point at which combustion ceases, thereafter the material progressively cools until it reaches the bottom of the shaft where it is discharged through the rotary grate into the discharge chute 4. This second point represents the. boundary between the combustion zone 'B and the cooling zone C.

Blast air is introduced into the shaft 2 at the bottom of the cooling zone C through the opening 6 in the top of the discharge chute 4 and through the rotary grate 3, the quantity of air supplied being usually such as to ensure adequate combustion of the solid fuel. If, according to the invention, an additional amount of air is introduced into the bottom of the cooling zone, it follows that the material will be discharged from the kiln at a considerably lower temperature, 'due to the cooling effect of the excess air.

In order that only that amount of air required for adequate combustion of the :solid fuel shall therefore reach the combustion zone, a proportion of the blast air :so supplied to the cooling zone is later removed from the cooling zone by means provided for that purpose. .As the blast air ascends the shaft 2 a, proportion of the air escapes from the lower part of the cooling zone C through the outlets '22, into the manifolds l4, and eventually into the escape conduit Hi. This air carries with it a quantity of heat abstracted from the material in the lower part of the cooling zone '0. As the remaining air ascends still further it absorbs a further quantity of heat from the cooling zone C. A further proportion of the blast air can be removed from the upper part of the cooling zone C through the outlets [-2 into the manifolds M through the "proportioning valves 1-3. The amount of air so removed is controlled by ther mo-couples 21 in conjunction with the thermoelectric regulator 28 which is connected to the proportioning valves 13. In this way the boundary between the cooling zone C and-the combustion zone B may be maintained at a predetermined height or the whole zone or sections of it maybe adjusted upwards or downwards as desired. V

A proportionof the blast air removed from the "cooling zone may, if desired, be returned to the combustion zone B, through a part or through all of the inlets 20, leading into the combustion zone in order to equal-ise the combustion around the periphery, the amount of air so returned -being controlled'by "the thermocouples 21 in conjunction with the regulator 28. A'further proportion of the blast air may be returned to the heating zone A, thereby returning heat abstracted from the lower or cooling part to the heating or upper part of the system. This air enters the heating zone A through "the inlets l8 and the proportioning valves '19 which are controlled in like manner as described above, by a further pair of thermocouples 2! and the regulator 28.

The remaining portion of the blast air removed from the cooling zone, and which is at a substantially high temperature, may be allowed to escapeto atmosphere through the escape conduit 15 and control valve 16, or it may be used for heating or drying purposes outside the kiln. In the present case the remaining portion of hot blast air is conducted through the escape conduit l5 and the control valve I15 to the drying chamber 23 from which it passes through the outlet 24 into the chimney I0.

By virtue of this arrangement the nodules or briquettes may be pre-dried by passing them through the drying chamber on the feeding conveyor 25 before discharging them through the chute 26 into the hopper I. In this way therefore, a substantial amount of heat, which would otherwise be wasted is returned to the system, thereby reducing waste heat to a minimum and as a result considerably improving the operating efficiency of the kiln.

The kiln may, for example, have a height of some 30 feet and an internal shaft diameter of some seven feet, and may be charged at the rate of tons per hour, with nodules or briquettes of the following composition: 11.7% silica, 5.6% alumina, and iron oxide, 36.3% lime, and 45.3% solid fuel. The air blast may then be adjusted so that come 6000 cu. ft. 1: er minute passes directly upwards from the cooling zone C to the combustion zone B whilst up to a further 6000 cu. ft. per minute is diverted from the cooling zone C and further employed in the manner described.

Whilst specific figures of dimensions, compositions, quantities of air and rates of charging have been given, solely by way of example, it should be understood that they in no way are binding and may be varied considerably depending on circumstances.

What I claim is:

1. A method of operating a vertical shaft furnace in which discrete material comprising solid fuel is charged at the top of the shaft and passes down said shaft in countercurrent to an ascending air blast introduced at the bottom of said shaft to form within said shaft a preheating zone near the upper end, a cooling zone near the lower end and a combustion zone intermediate but adjacent said other two zones, comprising the steps of supplying said air in an amount in excess of that needed to obtain adequate combustion of said solid fuel in said combustion zone and removing from the periphery of the upper part of said cooling zone that part of the ascending air blast introduced at the bottom of the shaft which is in excess of the amount needed for combustion of the said solid fuel in said combustion zone so that a greater amount of air passes through the cooling zone than through the said combustion zone whereby the cooling of the material in the cooling zone i accelerated and a substantially uniform depth of the combustion zone is obtained.

2. A method of operating a vertical shaft cement kiln associated with a drying device for briquettes or nodules comprising cement forming material and solid fuel comprising the steps of charging from said drying device briquettes or nodules into the top of said kiln, introducing into said kiln from the bottom thereof an ascending air blast to establish within said kiln a preheating zone near the upper end, a cooling zone near the lower end and a combustion zone intermediate said other two zones, the amount of air introduced into the kiln being in an amount in excess of that needed for adequate combustion of said solid fuel in said combustion zone, adjusting the amount of air passing through the combustion zone to the amount needed for adequate combustion by removing part of the ascending air blast, before entering the combustion zone, from the periphery of the upper part of the cooling zone and supplying at least part of the air blast so removed to the said drying device and using it for predrying the nodules or briquettes before they are charged into the kiln.

3. In the method of operating a vertical shaft furnace in which discrete material comprising solid fuel is charged at the top of the shaft and passes down said shaft in countercurrent to an ascending air blast introduced at the bottom of said shaft and in which a preheating zone near the upper end, a cooling zone near the lower end and a combustion zone intermediate but adjacent said other two zones are formed, the steps of supplying said air blast in an amount in excess of the air needed to obtain adequate combustion of said solid fuel in said combustion zone, adjusting the amount of air passing through the combustion zone to the amount needed for adequate combustion by removing from the periphery of the upper part of said cooling zone a part of the ascending air blast, before entering the combustion zone, and introducing at least part of the air blast removed from said cooling zone to said preheating zone through peripheral. inlets such that a greater amount of air passes through the cooling zone than through said combustion zone.

4. In a vertical shaft furnace of the kind in which charging means are provided for supplying discrete material consisting at least in part of solid fuel to the upper end of the furnace and in which air supply means are provided for supplying at the lower end of the furnace an ascending air blast in excess of the amount of air needed for combustion of said fuel, said furnace including a preheating zone, a combustion zone below said preheating zone and an adjacent cooling zone below said combustion zone, outlet means for combustion gases at the upper end of the furnace above the preheating zone, discharge means for nongaseous combustion products at the lower end of the furnace below the cooling zone, at least one adjustable outlet passage arranged peripherally at the upper end of said cooling zone for discharging an adjustable part of the blast of air from the periphery of the cooling zone adjacent the combustion zone, and at least one inlet passage arranged peripherally of said preheating zone and connected to and communicating with said outlet passage at the upper end of said cooling zone whereby said adjustable part of the blast air is bypassed around and prevented from passing through said combustion zone.

5. In a vertical shaft cement kiln of the kind in which charging means are provided for supplying nodules 0r briquettes of solid fuel and cement forming material from a drying chamber directly to the upper end of the kiln, air supply means for supplying at the lower end of the kiln an ascending air blast in excess of the air needed for adequate combustion of said fuel, said kiln including a preheating zone, a combustion zone below said preheating zone and a cooling zone below said combustion zone, outlet means for combustion gases at the upper end of the kiln above the preheating zone, discharge means for the cement at the lower end of the kiln below the cooling zone, and at least one adjustable outlet passage arranged peripherally at the upper end of said cooling zone for discharging an adjustable part of the blast of air from the periphery of said cooling zone adjacent the combustion zone, said outlet passage at the upper end of the cooling zone being connected to and communicating with said drying chamber to dry the nodules or briquettes of solid fuel and cement forming material before being charged into the kiln.

6. In a vertical shaft cement kiln of the type comprising charging means for supplying nodules or briquettes containing cement forming material I and solid fuel to the upper end of the kiln and air supply meansfor supplyingan ascending air blast through said kiln from the lower end of: the kiln to establish a preheating zone in the upper part of the kiln, a cooling zone in the lower part of the kiln and a combustion zone intermediate said preheating and cooling zones and directly adjacent thereto, outlet means for combustion gases at the upper end of the kiln above said preheating zone and discharge means for the clinker at the lower endof the kiln, the provision of means for supplying said air blast in an amount in excess of the air needed for adequate combustion of said solid fuel in said combustion zone, of at least one adjustable outlet passage arranged peripherally at the upper end of said cooling zone for discharging an adjustable part of the blast of air from the periphery of the cooling zone adjacent thecombustion zone, whereby the cooling of the material in the cooling zone is accelerated and a substantially uniform depth of the combustion zone. is obtained and of inlet means arranged peripherally of said preheating zone and connected to. said outlet passage, whereby said adjustable part FRANCIS PAUL SOMOGYI.

References Cited in the file of this patent. UNITED STATES PATENTS Number Name Date 507,204 Bird Oct. 24, 1893 1,832,552 Haslam Nov. 17, 1,931 1,992,704 Lellep Feb. 26, 1935 2,199,384 Azbe May 7, 1940 2,245,664 Gronert June 17, 1941 2,345,067 Qsann Mar. 28, 1 944 FOREIGN PATENTS Number Country Date 487,256 Great Britain June 17,1938,