US2689786A

US2689786A - Process for the gasification of solid fuels

Info

Publication number: US2689786A
Application number: US132773A
Authority: US
Inventors: Hubmann Otto
Original assignee: Individual
Current assignee: Individual
Priority date: 1949-01-20
Filing date: 1949-12-13
Publication date: 1954-09-21
Anticipated expiration: 1971-09-21

Description

0. HUBMANN Sept. 2 1954 3; PROCESS FOR THE GASIFICATION OF SOLID FUELS Filed Dec. 13. 1949 INVENTOR 077a HUEMfl/V/V,

BY-%Md/ w/ ATTORNEY Patented Sept. 21, 1954 PROCESS FOR THE GASIFICATION OF SOLID FUELS- Otto Hubman n, Bad Hamburg, Germany I Application December 13, 1949, Serial No. 132,773

Claims priority, application Switzerland January 20, 1949 Claims. 1

The invention relates to a process for the gasification of solid fuels, i. e. coal, lignite, peat or fuel-briquets. The gasification of solid fuels in rotary grate gas-producers meets with diificulties when the process is carried out with fuel possessing considerable caking properties. These difiiculties are increased if the gasification is to be carried out under a pressure of several atmospheres, since under the influence of the higher pressures the caking properties are also increased and the usual stoking of the fuel-bed is not possible with a gas-producer operating under considerable pressure. Another difficulty in connection with the gasifioation of solid fuel is due to the fact that only coarsely granular fuels can be gasified with good results while with a small size material the yield is considerably reduced. With a greater proportion of dust in the fuel the gasification becomes practically impossible in a quiescent fuel-bed. These facts are of particular importance for plants for the synthesis of hydrocarbons or the like where the coal for the manufacture of synthesis gas has to be used in the state it comes from the mine, which means that it contains a considerable share of fine-grained parts and dust. Considerable efforts have been made to solve this problem by using the so-called 'dust-gasification process, but this method is hardly suitableifor coal rich in ashes and hard coal, since the pulverization of all the coal for the process wouldbe extraordinarily expensive, and furthermore difiiculties would arise during the gasification by the melting of ashes which can hardly be overcome when operating under pressure.

The present invention solves the described problem with regard to non-caking and dustcontaining as well as caking coals by means of a combination of the gasification of granular fuels in a compact or a bubbling fuel-bed with the gasification of the finely granulated and powdery parts of the fuel by way of dust-gasification, 1. e. suspended in the gas stream. It is advantageous with this process, according to the invention, to use a gas-producer which comprises in its lower part a fuel-bed and above that a zone of dust-gasification. In this way not only coarsegrained and fine-grained parts of the fuels can be processed in the same gas-producer but the gasification of strongly caking fuels can also be achieved since with the aid of the hot dust-gasification zone it becomes possible to eliminate the caking properties of the coarse-grained fuels in suspension or-at the surface of the fuel-bed to such an extent that operation with a quiescent 2 fuel-bed can be carried out without difiiculties arising from the well-known gas channels developing in the fuel-bed. Furthermore, the problem of discharging the liquid slag from the dust-gasification zone can be solved in this way since the liquid slag falls in drops on the fuel-bed and can be discharged together with the ashes of the fuels. It now becomes also possible to gasify the dust-like parts at such high temperatures that the composition of the gas with reard to the content of carbonmonoxide and hydrogen can be regulated to a great extent in order to meet the requirements of any kind of synthesis. Furthermore, when operating according to the invention, it becomes possible by an appropriate adjustment of the temperature above the fuel-bed to regulate the hydrocarbon con-' tents of the produced gas by cracking them to a larger or lesser degree, so that instead of heavier tars lighter hydrocarbons are produced as byproducts, or that with an extensive decomposition even with fuels with a high content of volatile constituents synthesis gas relatively poor in hydrocarbons can be produced directly.

For effecting the process according to the invention preferably a shaft-furnace is used, comprising in its lower part in the usual way a rotary grate for discharging the ashes. The fuelbed above the rotary grate is operated from below by the introduction of oxygen-containing media for gasificationf The downwardly arranged gasification chamber for dustlike fuels above the fuelbed is suitably supplied with solid fuels and an oxygen-containing gasification medium from above so that the gasification is carried out in suspension from above downward, and the gases leaving the dust-gasification zone intermingle with the gases rising from the fuel-bed, whereupon they are conducted in the usual way to the condensation plant.

Withnon-caking solid fuels it may be appropriate to feed the coarse-grained fuels into the fuel-bed from the side in order, for example, to increase the yield of by-products. Particularly with caking fuels, which can be gasified only after a considerable reduction of its caking properties, the coarse-grained fuels may, according to the invention, be also fed through the dust-gasification zone. The surface of the individual grains will then already be extensively heated while falling down and the grains are subjected to strong radiation when getting on the surface of the fuel-bed. The result is a fast coking of the coal without an appreciable amount of caking.

With strongly caking coal the formation of extensive agglomerations can be further reduced by the use of stirring arms operating within the fuel-bed, especially if, according to the invention, above the fuel-bed a cooled plate is arranged, on the upper surface of which another stirring arm .rotates. With this arrangement it may be even possible by appropriately shaping this plate, which may be fastened to the shell of the gas-producer, by means of cooled arms to break up any possibly occurring agglomeration of fuels before they reach the gasification zone below.

In carrying-out the process according to the invention liquid or gaseous hydrocarbons or similar substances as, for instance, gases containing methane or other hydrocarbons, as coke oven gas or waste gases from synthesis plants or tar-oils, mineral oils or the like, may also profitably be used for the production of gases consisting mainly of carbon oxide and hydrogen. Such substances need only be conducted through the dust-gasification zone, whereby they are cracked to a great extent. Proceeding in this way increases the security .of the dust-gasification process and facilitates the operation under considerable pressure, since any possibly occurring irregularity in regard to the dust supply would not lead to explosions for the reason that the oxygen is consumed sumciently by reacting with the hydrocarbons introduced as, for example, in the shape of hydrocarbon-containing gases. The introduction of gases makes possible the use of the process according to the invention, even if only finely granulated caking fuels without any appreciable content of dust are to be processed. The cracking of the introduced liquid or gaseous materials requires very high temperatures to be maintained in the space above the fuel-bed so that the finely granulated caking-coal continuously fed to the surface of the fuel-bed is in the same way heated suddenly and in a thin layer, thus preventing the formation of larger agglomerations. Even when operating without the introduction of hydrocarbons the danger of explosions is considerably decreasedby the process according to the invention for the reason that already before leaving the gas-producer any oxygen occurring in the dust-gasification zone will be consumed by the gases rising upward from the fuel-bed. V

For processing caking fuels it is, advisable to adapt the size of the grains of the coarsely granular fuels to' their caking properties. With strongly caking coal rich in gas one ,may, for

example, crush all the coal to'be processed to I a maximum'grain size of approximately 191mm. and to feed the whole charge including the dust from a storage bin uniformly to the gas-producer. One may,however, put the fuels through a sieve after crushing and feed the grains up to 1 mm. in size separately from'those of 1 to mm. size from two separate storage bins to the gas-producer. Another way of regulating the process of dust-gasification within'wide limits consists in apportioning the oxygen fed to the dust-gasification zone so that the composition of the gas to be produced as well as the influence of caking of the fuel and that of the cracking of the hydrocarbons can be adapted to a large extent to the desired yield. Further means for regulating the temperatures above the fuel-bed consists, according to another modification of the invention, in apportioning the gaseous or liquid hydrocarbons of foreign origin that are to be fed to the gas-producer. If only a limited cracking of the hydrocarbons is required the fuel-bed can be increased so as to extend above the lower rim of the dust-gasification-chamber, so that the hot gases from this chamber carry the destillation products downwards through part of the fuel-bed.

The apparatus according to the invention is shown on the accompanying drawing by way of example in the cross-section along the vertical axis of the gas-producer operating in this case under a pressure of 10 to 20 atmospheres for the production of hydrogen-containing gases for the synthesis of hydrocarbons or the like from caking coal.

The gas-producer I is provided with a waterjacket 2. It comprises in the lower part the installations for the gasification in a compact fuel-bed 3 and in the upper part a gas-chamber Q serving for the gasification of fuel dust and/or the cracking of hydrocarbons or the like. The fuel-bed is supported by a bottom-plate 5 above which a water-cooled rotary grate 6 is mounted in bearings on the hollow shaft l. The latter is fastened by means of several water-cooled arms 26 to the shell of the gas-producer. The rotary grate has an upward extension in the shape of a column carrying stirring arms 9. The column and the stirring arms are also fitted with watercooling as a protection against destruction by burning. Attached to the rotary grate S are one or more shoes H] for removing the residues of the gasification through the central opening in the bottom plate 5 into the ash-pit 23. The rotary grate is driven by the gearing H. By means of preferably hydraulically operated vertical valve 24 the residues of gasification are, for example, periodically discharged into the sluicing chamber situated below it.

The gasification means as, for example, oxygen and steam, are fed to the fuel-bed through line 12 and the opening i3. The water for cooling the rotary is fed through line it. The water flowing out of line M fills the hollow spaces provided in thestirring arms. The water chambers 23 and r 29 of the column 8 and those of the rotary grate The 6 are in communication with each other. steam developing from the water can flowout into the gas-producer through the central line 30 and through the openings i3 providedin the double wall of the column. In the upper part 7 of the fuel-bed, or below the dust-gasification zone A respectively, a plane watercooled plate ie is connected by three or more arms H5 with the Water-chamber 2 of the gas-producer. The coarse-grained part of the fuels falls onthis plate and is cokedjn a very short time. The stirring arms 9 above the plate shove this coked fuel continuously into the fuel-bed. Larger agglomerationsfloffuels forming on the plate can; if necessary, be crushed to a size suitable for gasification byanjappropriate shape and arrangement of the rotating arms it While they pass through them,

The gasification zone 5 is fitted with a refractory lining 11. At the upper part of the zone conveyer'worms It and 20 feed the powdery fuels from the bin [9 and the granular fuel from the bin 2| to the gas-producer. The bins are periodically refilled by means of pressure-resisting sluicing devices (not shown) ofcommonly known design.

Opening into the upper part of the dustgasification-zone 4 is a line 22 through which oxygen, or oxygen and steam containing mixtures, are introduced, preferably tangentially, so that an immediate turbulence of the concurrently entering fuel dust takes place whereby the fuel is considerably accelerated. In case of hydrocarbon containing gases or the like being disposable for decomposition they may be introduced either together with the fuel dust or at approximately half the height of the dust-gasification zone. If dust is not disposable the gases are preferably fed to the upper part of the gasproducer, where after entering in a whirling state they are brought to reaction with the oxygen necessary for cracking them.

The gases produced are discharged through opening 2'! and further processed for gaining byproducts and for cleaning in a condenser plant of known design. For the purpose of checking the gasification process and especially the coking and the height of the fuel-bed, a spy-hole 25 is provided, which is fitted with a strong heatresisting pane of glass. On the basis of the result of this checking the feeding of the solid fuels and especially the portion of coarsely grained fuels can be regulated.

Depending on the relative amounts of dust and granular fuels the dust-gasification may in some particular cases take place in the annular chamber of the upper part of the gas-producer, and the resulting gases from both zones are discharged centrally in an upward direction. The granular fuel is in this case preferably introduced centrally falling through the ascending discharging gases.

With the process and apparatus according to the invention it becomes possible to gasify directly in a gas-producer non-caking as well as caking fuels of widely different granular composition, including such with a large content of dust without the necessity of completely grinding them to dust previously. It also becomes possible to gasify fuel rich in ashes even at high temperatures without running the risk of having dificulties with sintering ashes, and it is further possible to regulate within wide limits the composition of the gases as well as the properties of the by-products to be gained by adjusting the operating conditions accordingly. In spite of the extensive adaptability of the process to almost any fuels the gasification can in all cases be carried out under pressure for example of 20 to 30 atmospheres.

What I claim is:

1. A process for the continuous gasification of solid fuel under at least atmospheric pressure in a shaft furnace which comprises introducing an oxygen-containing gas into a fuel bed of coarsegrained fuel in a lower zone of the furnace from below to gasify such fuel, simultaneously separately gasifying fuel dust in a suspended state in an upper zone of the furnace with an oxygen containing gasifying medium, withdrawing the gases emitted in both gasifying zones jointly from a portion of the furnace above the fuel bed and feeding the coarse-grained fuel to the fuel bed through the zone in which the fuel dust is gasified.

2. A process for the continuous gasification of solid fuel under at least atmospheric pressure in a shaft furnace which comprises introducing an oxygen-containing gas into a fuel bed of coarsegrained fuel in a lower zone of the furnace from below to gasify such fuel, simultaneously separately gasifying fuel dust in a suspended state in an upper zone of the furnace with an oxygen containing gasifying medium, withdrawing the gases emitted in both gasifying zones jointly from a portion of the furnace above the fuel bed, feeding the coarse-grained fuel to the fuel bed through the zone in which the fuel dust is gasified, and introducing into the last mentioned zone a hydrocarbon which is cracked in such zone.

3. A process in accordance with claim 2, in which said hydrocarbon is a fluid hydrocarbon.

4. A process in accordance with claim 2, in which said hydrocarbon is methane.

5. A process in accordance with claim 2, in which said solid fuel is a caking coal and the fuel bed is continuously broken up by agitation.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,027,290 Smith May 21, 1912 1,792,632 Dieterle Feb. 17, 1931 1,840,649 Winkler et a1 Jan. 12, 1932 1,855,034 Stryker Apr. 19, 1932 2,111,579 Winkler et al Mar. 22, 1938 2,126,150 Stryker Aug. 9, 1938 2,216,792 Stryker Oct. 8, 1940 FOREIGN PATENTS Number 7 Country Date 7,420 Great Britain Mar. 23, 1911 of 1910 OTHER REFERENCES GWF-Vol. 88, No. 5 (1947), pages 129 to 136.

Claims

1. A PROCESS FOR THE CONTINUOUS GASIFICATION OF SOLID FUEL UNDER AT LEAST ATMOSPHERIC PRESSUR IN A SHAFT FURNACE WHICH COMPRISES INTRODUCING A OXYGEN-CONTAINING GAS INTO A FUEL BED OF COARSEGRAINED FUEL IN A LOWER ZONE OF THE FURNACE FROM BELOW TO GASIFY SUCH FUEL, SIMULTANEOUSLY SEPARATELY GASIFYING FUEL DUST IN A SUSPENDED STATE IN AN UPPER ZONE OF THE FURNACE WITH AN OXYGEN CONTAINING GASIFYING MEDIUM, WITHDRAWING THE GASES EMITTED IN BOTH GASIFYING ZONES JOINTLY FROM A PORTION OF THE FURNACE ABOVE THE FUEL BED AND FEEDING THE COARSE-GRAINED FUEL TO THE FUEL BED THROUGH THE ZONE IN WHICH THE FUEL DUST IS GASIFIED.