US3218998A - Gasifiers - Google Patents

Description

1965 A. H. FAIRMAN ETAL 3,218,998

GASIFIERS Filed March 15, 1965 2 Sheets-Sheet 1 zw w Mw% W Attorneys 7 Nov. 23, 1965 FAIRMAN ETAL 3,218,998

GASIFIERS 2 Sheets-Sheet 2 Filed March 15, 1963 II [III I] Attorneys United States Patent "ice 3,218,998 GASIFIERS Albert Henry Fairman, Oc'kham, Woking, Surrey, Donald Richard Henry Fryer, Ashtead, Surrey, Standish Masterman, London, and William Alexander Peet, South Croydon, Surrey, England, assignors to Minister of Power, in her Majestys Government of the United Kingdom of Great Britain and Northern Ireland, London, England Filed Mar. 15, 1963, Ser. No. 265,446 Claims priority, application Great Britain, Mar. 21, 1962, 10,811/ 62 2 Claims. (Cl. 110--165) This invention relates to the production of gas in continuously slagging fixed bed gasifiers using solid fuels such as coal, coke, lignite and similar materials.

An object of the present invention is to prevent, in a more efficient manner, not only the clogging of the slag outlet from the hearth of a gasifier, but considerably to reduce the passage of fuel through this outlet.

In slag-forming gasifiers, it is well known practice to quench the molten slag in water, thereby to cause it to break up in the granular form termed frit.

The invention is applied to a slagging gasifier having a slag outlet passage through which molten slag will drain from the hearth, and a burner, exterior to the hearth, for projecting, from a location offset from the path down which the slag will drain from the said outlet passage, a jet of flame into the said outlet passage, thereby to maintain the slag in a sufliciently fluid condition.

Within the part of the hearth of a gasifier into which the tuyeres direct the gasification medium, or blast, which may enter the hearth with a considerable velocity, there is considerable movement of fuel, which may be greater or less according to the velocity of the blast, and because of this movement this zone in the hearth is known as the raceway.

According to the invention, a gasifier as just described, is provided with a muffle, offset from the path down which the slag drains from the aforesaid slag outlet passage. This muffle is so arranged that the flame from the said burner will pass through it on its way to the slag outlet passage, in order that dispersion of hot gas from the flame will be substantially reduced to enhance the effect of these gases in not only maintaining a clearance through the said outlet passage for the slag by preventing descent therethrough of particles of solid fuel from the hearth, but also in maintaining open conditions for the flow of slag from the raceway to the said outlet passage. The burner, muffle and slag outlet passage may be inclined with respect to the path down which will fall the molten slag from the said outlet passage. Preferably the entry to the muflle is sealed around the burner.

A preferred construction of gasifier according to the invention will now be described with reference to the accompanying drawings of which:

FIGURE 1 is a sectional elevation.

FIGURE 2 is a fragmentary sectional view showing certain parts to a larger scale.

The gasifier illustrated in the accompanying drawings comprises an outer casing 1 of more or less orthodox 3,218,998 Patented Nov. 23, 1965 cylindrical design surmounted by a fuel inlet dome 2 into the upper end of which dome fuel, with or without flux, may be introduced, through an inlet 2a, from a lock hopper (not shown), the lower end of this fuel inlet dome 2 merges into the supper end of a cylinder 3, the lower portion of which cylinder is sealed into the upper end of the casing 1. Provided near the upper end of the casing 1 is a radial outlet 4 for the gas, to which outlet may be connected a pipe (not shown) leading to a scrubber (not shown) and a cyclone scavenging chamber (not shown) for removing any solid particles from the gas, the exit from which scavenging chamber is connected to a main (not shown).

The hearth of the gasifier, which hearth is indicated by 5, is carried within an inner cylindrical container 6 which is concentric with the outer casing 1 and extends upwardly, from about halfway up this casing, to a level slightly below that at which is situated the gas exit 4, and this inner container 6 tapers outwardly at its upper end portion towards the outer casing 1.

The inner container 6 is also provided with a refractory lining, indicated generally by 7, and at its lower end this lining rests upon a flange 6a provided around the interior of the container 6. The upper end of the refractory lining 7 extends up to a level in close proximity to the lower end of an insulating refractory lining 8 at the upper end portion of the gasifier and in part carried in a temperature resistance refractory lining 8a. From the foregoing description it will be appreciated that the inner cylindrical metal container 6 is of somewhat lesser external diameter than the internal diameter of the outer casing 1, so that an annular space 9 is formed between the casing 6 and the outer casing 1. The bottom of the hearth 5 is carried upon a horizontal plate 10 forming the bottom of the container 6.

Provided at diametrically opposite points of the wall of the outer casing 1 and slightly above the level of the bottom of the hearth are openings 11, 11, within each of which is welded the inner end portiton of a tuyere insertion chamber 12, each of which chambers 12 is closed at its outer end by a tuyere access cover 13 through which passes a tuyere 14 the inner end of which tuyere projects through and is sealed into a suitable opening 15 in the wall of the inner tubular metal container 6 and thence passes through the refractory lining 7 to a point above the bottom of the hearth but does not extend to the axis of the gasifier. The tuyere insertion chambers 12 are circular in cross-section. Each of the tuyeres 14 inclines downwardly toward the bottom of the hearth and is adapted to receive the gasification medium, for example oxygen, air, and steam in appropriate proportions. The tuyeres 14 are double walled and are provided with pipes 14a through which cooling water may be supplied for passage between the walls of these tuyeres, and with pipes 14b for the exit of this water into the respective tuyere insertion chambers 12 from which this water passes in a manner to be hereinafter described.

Welded or otherwise secured in a gas-tight manner to the underside of the plate 10 at the lower end of the inner tubular metal container 6 is the upper end of a coaxial tube 16 which is of somewhat smaller diameter than the said tubular container. This tube 16 extends about one third of the way down the lower half of the outer casing below the plate 10 and is around its lower end sealed to the inner circumference of a centrally perforated flexible disc 17 the other portion of which disc is sealed to the inside of the outer casing 1 the arrangement being such that an annular space, closed at its lower end, is formed between the tube 16 and the outer casing 1, which space, at its upper end, is continuous with the lower end of the aforesaid annular space 9 formed between the inner tubular container 6 and the outer casing 1. The flexible disc 17 thus forms a seal at the lower end of the said continuous space which seal permits of relative expansion or contraction axially between the casing 1 and the assembly comprising the inner casing 6 and the tube 16.

The plate 10 is provided with an opening 18 which opening is, at one side, provided with a downwardly inclined metal lip 19. Carried upon the plate 10 and lip 19 is a layer 20 of refractory material which layer extends downwardly beyond the lower edge of the lip for a short distance, and a part of which layer 20 bridges a part of the opening 18 in the said plate to an extent such as to form with part of the refractory-bearing lip 19 an inclined passage 21, which passage, as will be hereinafter more fully described, forms an exit for molten slag from the hearth.

Disposed within a bush 22 welded into the tube 16 is a bush 23, through which latter bush extends and is sealed into the inner end portion of a tube 24 and the inner end portion of a tube 25. The tubes 24 and 25 pass out from the gasifier through a sealing bush, indicated by 26, in the casing 1, and the purpose of these tubes will be described hereinafter.

Formed upon the underside of a part of the refractory layer 20 and depending through the opening 18 of the plate 10 is a mufile 27 of refractory material, which muffle is constructed integrally with the said layer. This mufile is so disposed that the inner end portion of the bush 22 passes through and is sealed into a wall which closes one end of this muflie, so that the inner end portions of the tubes 24 and 25 are directed toward the lower end of the inclined passage 21, to which is also directed the open end of the mufiie 27, sufficient space being allowed between the open end of the muflle and the aforesaid part of the layer 20 which overlaps the lower end of the lip 19 for molten slag to fall from this part and not enter the muflle.

The purpose of the tubes 24 and 25 is to form within the muflle 27 a burner which has an improved performance in maintaining the slag fluid, in considerably reducing descent of particles of solid fuel from the hearth through the slag outlet passage, and in maintaining open conditions for the flow of slag from the raceway to the said outlet passage, by virtue of the fact that the muffle substantially reduces dispersion of hot gas from the burner flame. Liquid fuel could, for example, be passed through the tube 24, and air for the combustion of this fuel could be passed through the tube 25.

In the refractory layer 20 of the bottom of the hearth there is embedded a pipe 28 bent into the form of a substantially flat coil through which cooling water may be passed.

The mufile 27 has embedded in its wall a cooling water pipe 29 coiled into the form of a helix, and the lower part of the inclined passage 21 has a similar cooling coil, indicated by 30, the refractory lining 7 of the inner container 6 also having embedded in it upper and lower cooling-water coils, indicated respectively by 31 and 32.

Pipes for the supply of water to the various cooling coils just described are shown as passing through a sealed chamber 33 upon the lower part of the casing 1. The coiled pipe 28 is formed in three sections to each of which sections water can be supplied through a pipe 34, and the exit from each of these sections is through a pipe 35 4 which passes through the wall of the tube 16 and discharges in this tube. Water is fed to the cooling coil 29 through a pipe 36, and leaves this coil by a pipe 37, water being fed to the coil 30 through a pipe 38 and leaving this latter coil by a pipe 39.

The upper coil 31 is supplied with water through a pipe 40, which water leaves this coil through a pipe 41 which discharges into the annular space formed between the tube 16 and the casing 1, water being supplied to the lower coil 32 through a pipe 42 and leaving this coil through a pipe 43 which also discharges into the said annular space. This discharge of water from the pipes 41 and 43 into the said annular space causes water to be supplied not only to this space but to the aforesaid space 9 which is in communication therewith. Extending up diametrically opposite parts of the annular space 9 is a pair of vertical pipes 44, 44, each having an outlet 45 just below a respective tuyere insertion chamber 12. These pipes 44 serve to discharge, in a manner to be hereinafter described, the cooling water which has entered the bottom of the aforesaid annular space from the outlet pipes 41 and 43 of the respective upper and lower coils 31 and 32 and passed to the upper part 9 of this space, also water which has discharged into the tuyere insertion chambers 12 from between the double walls of the tuyeres, by way of the pipes 14b.

Arranged concentrically within the lower end of the casing 1 of the gasifier is a tank 48 having a flat top with a central opening 49 around which is attached the centrally perforated part of a conical dish 50. Passing up through the wall of the casing 1, into which it is sealed, and similarly through the wall of the tank 48, is a water supply pipe 51, which passes nearly up to the upper wall of the tank and is turned over hookwise at its upper end so that liquid issuing from it will be projected downwardly within the tank. Also passing through the wall of the lower end of the casing 1, in which it is sealed, is a draw-off pipe 52 having at its upper end a horizontal portion 52a which extends radially over the dish 50, the inner end of this portion 52a being bent down slightly into the dish.

The whole of the system just described works in a completely submerged condition, because, when the gasifier is operating, the water level is maintained fairly well up the inside of the tube 16, so that molten slag which falls from the refractory covered lip 19 will be quenched in this water, and the frit, formed as a result of this quenching, will pass down through the water and into the dish 50, where, due to the current produced by the water flow from the supply pipe 51 and into the draw-off pipe 52, flotation of frit will take place, and the suspended frit of the required particle size will be sucked-off into the pipe 524 Should any larger particles of slag be formed or any lumps of iron be formed by reduction of iron oxide in the ash of the fuel, these will pass into the tank 48, means (not shown) being provided whereby they can be discharged in any suitable manner, for example by a lock hopper. In such an arrangement as just described, the pipe 51 could be connected to the output side of a pump (not shown), the intake side of which pump could be connected to the output side of a closed separator tank (not shown), the input side of which separator tank could be connected to the draw-off pipe 52, so that when the pump is operating, a strong current of water will circulate through the system. A second separator tank could be provided which could be so arranged with respect to the first separator tank that these tanks could be brought into operation and emptied alternately.

The gasifier is provided with a water level indicator 53, the lower end of which is connected to a chamber 54 which is similarly arranged in the wall of the casing 1 to the chamber 33 and diametrically opposite thereto. The upper end of the water level indicator 53, is connected to the tube 16 by a pipe 55 which passes through a tube 56 carrying a sight glass, the inner end of which tube 56 is sealed around an observation opening in the wall of the tube 16, the tube 56 passing outwardly through and being sealed into the casing 1, the arrangement being such that the slag flow from the refractory covered lip 19 may be viewed through the tube 56.

The aforesaid pipes 46 are connected at their lower ends to the lower end of a pipe 57 which passes upwardly through a sealing gland 58, into the lower end of the casing 1 and is sealed at its upper end by the bottom of the tank 48, the upper end of which pipe 57 forms a central support for the said tank, while the exit from this pipe comprises a lateral perforation into which is connected the lower end of a pipe 59 the upper end of which discharges substantially at the level of the top of the dish 50.

Fixed upon the lower end of the cylinder 3 within the upper part of the gasifier is a tubular body 60 the upper part of which is of a constant diameter and the part below this is frust-o-conical, the purpose of this body 60 being to control the flow of fuel into the gasifier and also to prevent its passage into the gas outlet 4.

Provided upon the upper part of the dome 2 is a bush 61 the purpose of which is to permit the insertion into the gasifier of a gas sampler 62.

In the case of the gasifier being operated at high pressure, cooling water would be supplied to the cooling coils at a pressure such that the water pressure at the outlets from these coils would be consonant (having regard to the pressure drop along these coils) with an average pressure throughout these coils suflicient substantially to offset that within the gasifier, this same principle, of course, also applying to the water within the aforesaid annular space of which the space 9 forms the upper part.

By the employment of suitable water-cooling means in the tuyeres 14, these can be made to have a satisfactory length of life at the pressures employed to operate the gasifier. Alternatively the gasifying agents, e.g. steam and oxygen, may be passed through the tuyeres at a sufii-ciently high velocity to achieve a suitable heat transfer to maintain the material of which the tuyeres are made well below its yield point.

Provision may be made whereby the size of the slag hole 21 is adjustable. This may be effected by forming the slag hole between horizontal parallel tubes which are eccentric or carried upon eccentrics so that their rotation will enable the dimension of the hole to be varied.

If desired, a device may be provided for chopping-off any slag incrustation at the slag hole. Such a device is shown generally in the drawings as a knife 63 forming part of a lever 64 pivotally mounted within a bracket 65 carried beneath the plate 10 and actuated by a piston (not shown) in a cylinder (also not shown) supplied with compressed gas.

66 is a pipe through which the lower part of the gasifier can be periodically purged.

From the foregoing description it will be understood that the optimum conditions of operation would be such that not only would the slag be kept sufliciently hot by the burner to be in the requisite fluid condition, but such that the products of combustion from the burner would pass up the slag outlet passage and maintain an opening through this passage which is free from solid fuel and solidified slag. The conditions of operation before and during gasification would also preferably be such that the products of combustion from the burner would maintain a space within the hearth in front of the tuyeres, to facilitate drainage of slag from the raceway. In order to achieve this the burner gases must have a minimum momentum. As an example, with a tap hole 3 inches in diameter and at a pressure of 45 p.s.i. the burner gases will preferably have a velocity greater than 50 feet per second.

The quantity of slag flowing through the hearth and slag hole may be controlled, to achieve an optimum rate of flow, by recirculation of fritted slag with fuel charged into the gasifier. This recycled frit may undergo certain preparation before being reintroduced into the gasifier, such, for example, as being mixed with a binding material or subjected to a pelleti-ng process.

The producer may be started up by using the slag hole burner as the primary source of heat to heat up the fuel in the fuel bed in front of the tuyeres to a temperature at which it will ignite when air is supplied through the tuyeres and/or the slag hole, e.g. by means of a cornpressor or by an eductor fitted in the make gas line.

The aforesaid burner may be provided with electrical means, for example, a sparking plug, for lighting it to start the furnace. Instead of using a sparking plug, a pyrotechnic may be employed within the fuel bed for starting under pressure.

The performance of the gasifier may be indicated and/or controlled by means of a radiation pyrometer (not shown) positioned in one of the tuyeres. This pyrometer could, for example, be located at the outer end of a quartz rod (not shown) disposed in the tuyere so as to act as a waveguide to the pyrometer. In such an arrangement, the pyrometer could, for instance, be arranged to control, through suitable means, the rate of gas production by regulating the passage of steam and oxygen through the tuyeres.

When it is necessary to transfer fuel from the lock hopper into the fuel inlet dome, this may be indicated by means of a radio-active source at one side of the tubular portion immediately below the dome and a detector at the diametrically opposite side of this portion, the arrangement being such that, when there is fuel in this tubular portion this will obstruct the passage of rays from the radio-active material to the detector. Alternatively, the detector could be arranged to initiate the transfer of fuel from the lock hopper automatically, also the refilling of the lock hopper after this transfer.

If desired, the dust carried over with the make gas and separated from this, for example, by means of a cyclone separator may be briquetted or otherwise con- V8I1Z6d into an aggregate fuel with or without binders and then returned to the bed of the gasifier.

If necessary, suitable agents may be added to the solid fuel charges, so that the sulphur containing compounds alre combined with fluxing agents and pass out with the s ag.

Various modifications can be made to the apparatus without departing from the invention,v For example, the lower part which includes the portion where the frit is formed, may be made as a unit separate from the gasifier and suitably connected thereto.

Another modification may concern the fuel feed to the gasifier, whereby, with the aid of a distributor, the fuel may be evenly spread upon the column already in the gasifier.

A further modification may permit the introduction of fuels such as pulverised fuels, oil or fuel gases through the tuyeres where the supplementation of the fuel normally used in the fixed bed of the gasifier is desirable for economic or other reasons.

We claim:

1. In a slagging gasifier having a hearth formed with a slag outlet therein the lower part of which outlet has a depending downwardly inclined lip from which will drain molten slag received from within said gasifier, and which gasifier also includes a burner disposed below the hearth and offset from the path down which the slag will flow, for maintaining the slag sufficiently fluid; the im provement which comprises a muffle disposed at the underside of the hearth and extending therealong to a point near to and opposite the said lip, which muffle is directed substantially horizontally toward said inclined lip and carries the burner so that the flame and a jet of hot gases will be projected from the burner, directly along this muffle, onto the slag upon the lip, and upwardly there- 7 8 along, thereby at the same time substantially preventing 2,033,685 3/1936 Coutant 110-28 descent of solid fuel from the hearth and so maintaining a free passage for the slag. FOREIGN PATENTS 2. A slagging gasifier as claimed in claim 1, wherein 737,151 9/1955 Great Britain the muflle is tubular and the end thereof remote from the 5 749,632 5/1956 Great Britain slag outlet is sealed around the burner.

References Cited by the Examiner UNITED STATES PATENTS JAMES W. WESTHAVER, Primary Examiner.

References Cited by the Examiner UNITED STATES PATENTS 1,452,045 4/19231 Hawley 11028 10

Claims (1)

1. IN A SLAGGING GASIFIER HAVING A HEARTH FORMED WITH A SLAG OUTLET THEREIN THE LOWER PART OF WHICH OUTLET HAS A DEPENDING DOWNWARDLY INCLINED LIP FROM WHICH WILL DRAIN MOLTEN SLAT RECEIVED FROM WITHIN SAID GASIFIER, AND WHICH GASIFIER ALSO INCLUDES A BURNER DISPOSED BELOW THE HEARTH AND OFFSET FROM THE PATH DOWN WHICH THE SLAG WILL FLOW, FOR MAINTAINING THE SLAG SUFFICIENTLY FLUID; THE IMPROVEMENT WHICH COMPRISES A MUFFLE DISPOSED AT THE UNDERSIDE OF THE HEARTH AND EXTENDING THEREALONG TO A POINT NEAR TO AND OPPOSITE THE SAID LIP, WHICH MUFFLE IS DIRECTED SUBSTANTIALLY HORIZONTALLY TOWARD SAID INCLINED LIP AND CARRIES THE BURNER SO THAT THE FLAME AND A JET OF HOT GASES WILL BE PROJECTED FROM THE BURNER, DIRECTLY ALONG THIS MUFFLE, ONTO THE SLAG UPON THE LIP, AND UPWARDLY THEREALONG, THEREBY AT THE SAME TIME SUBSTANTIALLY PREVENTING DESCENT OF SOLID FUEL FROM THE HEARTH AND SO MAINTAINING A FREE PASSAGE FOR THE SLAG.

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