US3311460A - Method for gasification of carbonaceous materials - Google Patents

Description

March 28, 1967 H. H. STOTLER ETAL 3,311,460

METHOD FOR GASIFICATION OF GARBONACOUS MATERIALS original Filed'Jan. 4, 1962 FIGA //V l/E/V 70H5 United States Patent O 3,311,460 METHOD FR GASIFICATQN OF CAR- BGNACEDUS MATERIALS Harold H. Stotler, Westfield, NJ., George B. Farkas, Jackson Heights, N.Y., and Percival Cleveland Keith, Peapack, NJ., assignors to Hydrocarbon Research, Inc., New York, N.Y., a corporation of New Jersey Original application Ian. 4, 1962, Ser. No. 164,306, now Patent No. 3,226,204, dated Dec. 28, 1965. Divided and this application Aug. 11, 1965, Ser. No. 487,646 3 Claims. (Cl. 48-197) This application is a division of our application S.N. 164,306, filed I an. 4, 1962, for Baffled Reactor, now U.S. Patent No. 3,226,204, dated Dec. 28, 1965.

This invention relates to improvements in reactors of the type which are primarily adapted for carrying out high temperature and high pressure gaseous reactions in the presence of a iluidized bed of particulate solids. It is an improvement on the invention disclosed in the patent of Keith, 2,995,426, of Aug. S, 1961.

The eorts to fluidize relatively fine powders such as iron oxide or coal with gases at high temperatures and high pressures, as for the purpose of reduction and gasification, has developed some unusual problems of maintaining uniform flnidity, avoiding rat-holing of gases, avoiding the formation of bubbles that cause objectionable tremors, avoiding the formation of ash clinkers and obtaining a uniform gas-solids contact.

While it was known that partitioning the mobilized layer with substantially vertical surfaces was effective in certain cases as, for example, when the iluidized bed did not exceed about five feet in depth and was usually about one foot in depth, it was only after subsequent studies of the problem that it was found lpossible Vto maintain unusually good gas-solid contact in beds of at least eight feet in depth As commercial practice required the vdeeper beds, this became of substantial importance.

The foregoing Keith patent is based on the discovery that in a iiuidized bed of this type (such as the gasification of coal nes or the reduction of iron oxides nes) fluidity at elevated temperatures and pressures can be maintained when the extended surface in the iluidized reaction zone, including the area of the walls of the reaction zone, is in the range of from four to twelve square feet for each cubic foot of the uidized bed.

In the gasification of coal it has been found that powdered coal is somewhat easier to fluidize than iron oxide powder and that the extended surface can be reduced to four square feet for each cubic foot of tiuidized bed which has the advantage of reducing capital expenditure.

In accordance with our invention, we have found that the geometry and construction of such batiles, Within such extended surface limitation, must be such as to prevent any accidental accumulation of nes and to permit the necessary free flow of particles which tend to move laterally as well as vertically in a fluidized bed.

More specifically, it is the object of our invention to provide a reactor for high temperature, high pressure fluidized reaction which is of a commercial size in diameter and height and having an internal baffling which is adapted to maintain a gassolids contact comparable to small laboratory scale results.

Another object of our invention is to provide a baffle structure for a iluidized reaction which structure has sufcient mechanical strength to maintain its shape at temperatures in the order of 1800 F. and which gives an extended surface, together with the Wall area, of from four to twelve square feet of surface for each cubic foot of bed and permits completely free movement of the fluidized particles in their customary flow paths.

A particular object of our invention is to provide a 3,311,460 Patented Mar. 28, 1967 baflie having Y shaped baflie elements for a fluidized reactor in which the baille itself is laterally open to particle ow but vertically continuous to maintain fluidity of solid particles.

Further objects and advantages of our invention will appear from the following description of preferred forms of embodiment thereof when taken with the drawings attached which are illustrative thereof and in which:

FIG. 1 is an elevation, with parts in section of 4a reactor for high temperature uidized reactions.

FIG. 2 is a horizontal cross section taken on the line 2 2 of FIG. l.

FIG. 3 is a vertical cross section through the lower part of FIG. 1 showing the detail of mounting of the balile.

FIG. 4 is a schematic horizontal section of a modified form of reactor having a multiplicity of bales.

The reactor 10 of FIG. l comprises a cylindrical vessel having a dished top 12 and bottom 13. Conveniently, the reactor 10 is supported on a cylindrical extension or skirt 14 projecting below the bottom 13 and its associated elements. Such an extension 14 is usually provided with access openings (not shown) and is of suicient height to give the desired headroom under the reactor.

The shell of the reactor 10 may conveniently be divided into a plurality of sections Ias suggested by the ange elements 15 to subdivide the reactor into a plurality of reaction stages or zones. However, for the purposes herein, the reactor 10 may be considered to have a vertically continuous internal chamber to form a vertically continuous iluidized bed. On a commercial scale, this would be ya bed of from five to fty feet in height when fluidized and usually would have a diameter of from one to ten feet.

Finely divided solids may be introduced to this chamber in -any desired manner as through the side inlet 16 and they will rest on the perforated bottom plate 17 except, of course, when the gases maintain the bed in a uidized or suspended condition. The fiuidizing gases such as oxygen 4and steam enter as through gas inlet 18 below the bottom plate 17 as shown in FIG. 3 so that the gas passing up through the perforated plate 17 will b-e uniformly distributed across the bottom of the reactor. Solids may be drained from thesystem at 20.

As is well known in the fluidizing art, the velocity of the gas can be regulated to maintain either a dense phase or a disperse phase iiuidized bed. This is Ia function of the particle size and density as well as the velocity and density of the gas. Usually, an expansion is desired which is suicient to assure complete gas contact with the particles without serious carryover. The reactant eiuent discharges from the upper part of the reactor as through outlet 22.

The react-or shown herein is adapted to be water-cooled and thus has an inner wall lining 24 forming a chamber to which water is suitably introduced as at 26 with the steam removed as at 28. A brick lining 29 is also customarily used on high temperature coal gasification operations.

With commercial size reactors as defined, we nd it necessary in order to maintain fluidization to use internal baffles which, as generally indicated at 30 in FIG. 2, are hereinafter described. It is to be pointed out that the area of the extended surface of these bafes together with the inner exposed wall of the reactor is of the order of four to twelve square feet per cubic foot of bed.

As shown in FIG. 2, the baffle 30 has a central core 32 from which webs -or blades 34 extend radially forming baile elements. These elements 34 are generally of Y shape in cross section with their outer branches 36 suitably secured to the outer branches of adjacent elements through cleats or filler plates 38. This thus tends to form a wheel shaped assembly one or more of which will extend over the entire cross section of the reaction zone depending on its size.

The respective blade or web portions are also relatively thin as compared to length to avoid any hold-up of solids. For elfective strength, the thickness is usually a small part of the total length.

Referring again to FIG. 1, it Will be seen that the central core 32 is preferably a series of vertically spaced discontinuous collars which thus do not impair horizontal intermixing of the particulate solids. Similarly, the cleats or ller plates 38 are also discontinuous and verticallyl spaced and merely maintain the desired spacing of the extended branch portions. Usually, we prefer to make the baffle sections 30 in several pieces, suitably mounted one on the other as with a bayonet type joint indicated at 40 in FIG. l.

In a commercial construction for coal gasication, the baffle members 30 are chrome lcastings adapted to be operated under temperatures in the order of 1800o F.

The invention is particularly suitable for the gasification of coal in silt form for the production of hydrogen. In such case, coal fines usually smaller than mesh are pre-treated as for drying and then blown into a coal feed bin which is adapted to discharge by gravity into -a coal hopper. By inert gas means, the powdered coal is then transferred by dense phase transport into the reactor 10 through line 16.

The reactor 10 for a commercial gasification of coal iines would have a tiuid bed of about ten feet in diameter and forty feet deep with a uidized density of 20 lb./cu. ft. (a settled bed of similar material is about 20 feet high with a settled density of 35-40 lbs./ cu. ft.).

Gasication of an anthracite coal nes containing 20% ash with preheated steam and oxygen in a uidized reactor as described herein operating at 450 p.s.i.g. and 1700 to 1800o F. will yield a product gas containing approximately 37.3% CO, 53.1% H2 and 9.6% CH@ The product is produced at a rate of 16,500 s.c.f.h. per square foot of reactor. This type reactor enables safe operation under pressure thereby resulting in production rates several times higher than can be achieved otherwise.

The amount of ash in the coal will vary within wide limits but we find that we can easily remove the ash as through side discharge line 42. These ashes will be suitably cooled in a well known manner. The minimum superficial velocity of gas as above mentioned will prevent the internal formation of clinkers.

In the gasification of coal, as well as in certain other reactions, we find it especially desirable to partially cool the eiuent gases to reduce the carryover of solid particles. As shown in FIG. 1, this may be accomplished with a typical internal heat exchanger 60 to which water may be fed at 62 and from lwhich the steam is removed at 64.

In certain tests that we have observed, we find that a reduction of temperature from about l700 F. to about 700 F. reduces the solids carryover to about one sixth of that at the higher temperature.

In a fiuidization operation such as coal gasification, it is very important that there be no place for a hang up of ash or agglomeration of coal particles. It will be noted that the webs 34 of the bathe `are not only widely spaced to -avoid any sharp corners or notches, but they are welded with fillets to give the exposed lcross section of the baffle a very free flowing aspect. Furthermore, with the vertically spaced collars 32 and ller plates 38, there is a complete freedom of the uidized particles to move laterally as Well as downwardly.

In FIG. 4 we have illustrated a reactor indicated at 50 with a series of baffles 52 and supplemental individual webs or blades 54. For uniform uidization throughout the cross section of very large reactors, it is desirable to adjust the baffle surface to obtain, as much as reasonably possible, a uniform spacing between baffles and conform to the ratio of four to twelve square feet per cubic foot of bed as hereinbefore referred to. In such case, supplementary open Y baffle elements, such as shown at 54, may be provided. These will be held in iixed position by suitable means, not shown. These supplementary elements may, of course, be heat exchange tubes if excessive heat is to be added or removed from the fluidized bed..

From a commercial standpoint, the economic production of hydrogen from coal is an important use of the hereinabove described reactor. However, this type reactor can be advantageously used in (l) the reduction of iron ores with hydrogen and/or carbon monoxide; (2) the gasification of carbon formed from the cracking of petroleum oils to produce hydrogen and carbon monoxide; (3) the hydrocracking of petroleum oils; (4) the hydrogenation of coal with hydrogen to produce a fuel gas -of reasonable B.t.u. value; (5) or any other process in which intimate contact of gases and solids are desired in a fluidized bed and lwhere the mechanical strength of the reactor internals are limited due to the temperature level of operati-on; (6) or any process in which localized heat is generated in one or more sections of the iluidized bed and it is desired to distribute this heat luniformly throughout the uidized bed.

In such cases the solids may be reactants such as coal lines or iron ore (iron oxides) to be reduced, or the solids may be typical catalysts as for hydrodesulfurization or hydrocracking or the solids may of course be inert contact surfaces. In each case, it is contemplated that they will have the typical neness characteristic of the particular process and in each case, adapted to be uidized by the owing gas.

In the reduction of iron ore nearly pure hydrogen is preferred as the reducing gas, temperatures of reduction are above 800 F. and pressures are usually in the order of 20D-450 p.s.i.g. as generally set forth in Keith et al. Patent 2,900,246.

Our invention is conceived to be of general application I'although primarily adapted to high temperature, high press-ure fluidized reactors. In view of the various modifications of the invention which will occur to those skilled in the art upon consideration of the foregoing disclosure without departing from the spirit or scope thereof, only such limitations should be imposed as are indicated by the appended claims.

We claim:

1. The process of gasification of carbonaceous solids with a gas at temperatures in excess of 1700 F. and at reactor pressures in excess of 50 p.s.i.g., wherein the reactor is provided with a vertically extending bae member having a plurality of continuous, laterally extending, blade portions having a minimum horizontal surface with reference to the length and width thereof, such blade portions extending substantially radially from the baffle member and being of substantially Y shape with the line of attachment of one blade portion to the bafe member being spaced from the line of attachment of the .adjacent blade portion to avoid any sharp corners and with the tips of adjacent Y portions stabilized with respect to each other, 4which comprises passing the gas upwardly through a bed of solids in contact with the baie member at a rate to cause mobility of said solids, the aggregate surface area of such baffle member being in the range of from four to twelve square feet per cubic foot of mobilized bed of solids, the blade portions being spaced one from another whereby the solids are free to move vertically and transversely with respect to said surfaces, cooling the reacted gas to a temperature in the order of 700 F. and withdrawing the reacted gas with a minimum of solids therewith.

2. The process of claim 1 wherein the carbonaceous solids are coal and the gas is an oxygen. and steam con.- taining gas.

J S 3. The process of claim 1 wherein the carbonaceous 3,004,839 10/1961 Tornquist 48-197 solids are coal and the gas is a hydrogen containing gas. 3,206,865 9/ 1965 McEntee 23-284 X 3,226,204 12/ 1965 Stotler et al. 23284 References Cited by the Examiner UNITED STATES PATENTS 5 MORRIS O. WOLK, Primary Examiner. 2,662,607 12/ 1953 Dickinson 48-206 JOSEPH SCOVRONEK, Assistant Examiner.

2,803,530 8/1957 Ludemau 48-206

Claims (1)

1. THE PROCESS OF GASIFICATION OF CARBONACEOUS SOLIDS WITH A GAS AT TEMPERATURES IN EXCESS OF 1700*F. AND AT REACTOR PRESSURES IN EXCESS OF 50 P.S.I.G., WHEREIN THE REACTOR IS PROVIDED WITH A VERTICALLY EXTENDING BAFFLE MEMBER HAVING A PLURALITY OF CONTINUOUS, LATERALLY EXTENDING, BLADE PORTIONS HAVING A MINIMUM HORIZONTAL SURFACE WITH REFERENCE TO THE LENGTH AND WIDTH THEREOF, SUCH BLADE PORTIONS EXTENDING SUBSTANTIALLY RADIALLY FROM THE BAFFLE MEMBER AND BEING OF SUBSTANTIALLY Y SHAPE WITH THE LINE OF ATTACHMENT OF ONE BLADE PORTION TO THE BAFFLE MEMBER BEING SPACED FROM THE LINE OF ATTACHMENT OF THE ADJACENT BLADE PORTION TO AVOID ANY SHARP CORNERS AND WITH THE TIPS OF ADJACENT Y PORTIONS STABILIZED WITH RESPECT TO EACH OTHER, WHICH COMPRISES PASSING THE GAS UPWARDLY THROUGH A BED OF SOLIDS IN CONTACT WITH THE BAFFLE MEMBER AT A RATE TO CAUSE MOBILITY OF SAID SOLIDS, THE AGGREGATE SURFACE AREA OF SUCH BAFFLE MEMBER BEING IN THE RANGE OF FROM FOUR TO TWELVE SQUARE FEET PER CUBIC FOOT OF MOBILIZED BED OF SOLIDS, THE BLADE PORTIONS BEING SPACED ONE FROM ANOTHER WHEREBY THE SOLIDS ARE FREE TO MOVE VERTICALLY AND TRANSVERSELY WITH RESPECT TO SAID SURFACES, COOLING THE REACTED GAS TO A TEMPERATURE IN THE ORDER OF 700* F. AND WITHDRAWING THE REACTED GAS WITH A MINIMUM OF SOLIDS THEREWITH.

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