GB2039458A - Reactor for the gasification of solid carbonaceous materials - Google Patents

Abstract

A reactor for the gasification of solid carbonaceous materials in a fluidized bed under elevated temperature and pressure conditions includes a distributor (40) being an elongate conduit which is mounted across the reactor chamber. At least the top portion of the distributor, when viewed in transverse cross-section, (fig. 3a) is formed by convergent surfaces (42) which form an upwardly directed apex preventing the deposition of reactor residues on the distributor. A cavity (41) for the hot gasification agent extend axially through the distributor and is connected with downwardly directed gas outlet apertures provided at spaced apart locations on the device. <IMAGE>

Description

SPECIFICATION Reactor for the gasification of solid carbonaceous materials The present invention relates to a reactor for the gasification of solid carbonaceous materials in a fluidized bed under elevated pressure and high temperatures. Reactors of this kind are being operated to an increasing extent under a high overpressure, for example 80 to 120 bar, and at a high temperature up to, for example, 950"C, since parameters essential to the gasification operation, particularly the reaction rate and the degree of gasification of carbon, cannot otherwise be brought to the values necessary for economical operation.

in fluidized bed generators operated under normal pressure, it is known to introduce the gasification agent, such as hydrogen, steam, oxygen-containing gases, into the space containing the fluidized bed through openings distributed around the periphery of the reactor. This requires the existence of a ring conduit and branch conduits outside the reactor. If the gasifier is operated under elevated pressure, feeding of the gasification agents in a conventional manner gives rise to difficulties.Since the gasification agent has to be introduced into the reactor at a pressure which lies at least slightly above the pressure prevailing in the reactor and, moreover, in order to cover the heat requirement, has to be preheated to a temperature which is generally not substantially lower than the temperature prevailing in the generator, very high demands have to be made with respect to the resistance to pressure and the thermal insulation of the feed lines for the gasification agent.

Consequently, it is an expensive matter to install the ring conduit and several branch conduits. Owing to the space required, it may not be possible to arrange corresponding lines, including the safety devices and the devices serving for thermal insulation, to an adequate extent externally on the reactor.

The aim of the present invention is to design a reactor of the type mentioned initially, which is suitable for gasification under high pressure and at a high temperature, such that the feeding of the gasification medium is simplified. A special aim is to reduce the expenditure on the feed lines, such that the feed lines are easy to survey and are thus readily controllable. It will be appreciated that the arrangement must be such that, despite the simplification, the state of the fluidized bed and the other conditions essentiai for reactions can be complied with and adjusted.

According to the present invention there is provided a reactor for the gasification of solid carbonaceous materials in a fluidised bed under elevated temperature and pressure conditions, comprising a feed device for hot gasification agent, which device takes the form of an elongate conduit which is mounted in a reactor chamber, across said chamber, at least the top portion of the device when viewed in transverse cross-section, being formed by convergent surfaces which form an upwardly directed apex, a cavity for said hot gasification agent, extending axially through said device, said cavity being connected with downwardly directed outlet apertures provided at spaced apart locations in said device.

Consequently, the distribution device for the gasification agent is shifted from the region outside the reactor to the interior space thereof. The difficulties described above are thereby largely avoided.

Care must be taken that the distribution device or devices leave free an adequately large crosssectional area through which the solid residues of gasification can be discharged downwardly and introduced into, for example, a cooling apparatus arranged therebelow.

Advantageously, the arrangement is such that the distribution device is in the form of a bridge, preferably made of a ceramic, which extends through the cross section of the reactor, preferably in a horizontal plane, and which extends through the crosssection of the reactor preferably along a diameter thereof.

Advantageously two distribution devices can be arranged in, for example, the same plane and can be combined to form a cruciform fitting, particularly when the reactor has a large diameter. Each device can then have an individual connection for the gasification agent fed from outside. However, it is also possible to provide both ends of each device with a connection of this kind. Alternatively, a plurality of distribution devices can be guided substantially parallel through the reactor chamber, in the same plane or in different planes.

When two or more distribution devices of this type are provided, they can be arranged in different vertical positions in the reactor and they will then not generally extend in the same vertical plane. Consequently, it would thus be possible to provide one or several distribution devices which substantially define the bottom boundary of the fluidized bed, and additionally to provide one or several distribution devices within the fluidized bed, that is to say, at a higher level. This would take into account the possibility, occurring in practical operation, of additionally blowing in, above a lower blowing-in plane, gasification agent or, optionally, other substances, into the reactor and into the fluidized bed in a region above its lower boundary.

In general it will be desirable for the gasification agent to emerge from all the outlet openings of the distribution device at substantially the same rate and in substantially the same quantity. This can be achieved without difficulty by making the total of the cross sections of all the outlet openings no larger, preferably slightly smaller, than the feed line cross section from which the outlet openings start.

The top of the distribution device should in all cases have sloping lateral surfaces, so that coal cannot be deposited thereon. By way of example, the cross section of the distribution device can be in the form of a triangle having an upwardly directed apex.

It will be appreciated that other cross sections can be chosen for the distribution device, care having to be taken that it has adequate stability under the conditions of gasification. The tubular cavity extending through the distribution device can be, for example, circular or alternatively, it can have an elongate cross section. When the reactor has a large diameter, it can be advantageous to support the bridge-like devices at one or several locations by, for example, struts leading through the wall of the reactor.

Advantageously, the distribution device or devices is or are arranged in the region of the transition between a lower downwardly conically tapering portion of the reactor and a substantially cylindrical portion disposed thereabove. That is to say, the solid residues of gasification normally accumulate in the conically tapering portion located therebelow.

The apertures provided in the distribution device forthe egress of the gas should generally be downwardly directed in order to prevent solid particles from entering the apertures. An advantageous construction has proved to be one in which the outlet apertures are disposed on both sides of, and along, a longitudinally extending axis or plane of the distribution device. The outlet apertures can be staggered relative to one another in the longitudinal direction of the device on opposite sides thereof, in order to ensure that the gasification agent emerging from the apertures is distributed as uniformly as possible over the cross section of the reactor.

The present invention will now be further described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a longitudinal section through a reactor constructed according to the present invention, Fig. 2 is a portion of Fig. 1, drawn to a larger scale; and Figs. 3a to 3c are cross sectional views of various embodiments of distribution device suitable for use in a reactor constructed in accordance with the present invention.

Referring to Fig. 1, the reactor 12 chiefly comprises a pressure-resistant casing 14 whose inside is provided in a conventional manner with a brick lining 16 of refractory material. The largest portion of the axial extent of the pressure-resistant casing 14 is surrounded by a second, external casing 18. The substantially annular space 20 located between the two casings 14 and 18 is filled with water which chiefly serves for cooling purposes. Alternatively, it is possible to arrange insulating material in the annular space 20 instead of water. These matters are however of no importance to the underlying concept of the present invention.

The carbonaceous material to be gasified is introduced into the interior space 24 of the reactor by means of a screw conveyor 22. Furthermore, at least one feed line 26 for the gasification agent, such as hydrogen, is provided. The feed line 26 enters the interior space 24 at a level below the level at which the coal is introduced into the reactor. The desired reaction between the carbon and the gasification agent takes place in a fluidized bed 28 which builds up in the bottom region of the reactor under the action of the upwardly flowing gasification agent. It will be appreciated that this does not preclude reactions also taking place in a secondary reaction chamber 30, located above the fluidized bed 28, between the gasification agent and the carbonaceous material and between the latter and the gasification products and possibly one with the other.Further, it is additionally possible to introduce media into the secondary reaction chamber 30. The resultant product gas is discharged from the reactor through the line 32 and fed to after-treatment stations in a conventional manner.

The solid gasification residues 34 from the fluidized bed 28 accumulate in the region above the level at which the gasification agent is fed through the line 26, and are discharged from the reactor 12 into a cooling apparatus (not shown in the drawings) located thereinbelow.

A distribution device 40 is provided in the interior space 24 of the reactor 12 at the transition between a central, substantially cylindrical region 36 and the bottom, substantially conical region 38. The device 40 extends diametrically across the circular transverse cross section of the reactor and is rigidly connected at both ends to the wall or the lining 16 of the reactor. The distribution device 40 is connected to the feed line 26 for the gasification agent.

Fig. 2 shows a detailed view of the distribution device 40 of Fig. 1, the device having spaced apart outlet apertures 46 distributed more or less along its entire length, i.e. over the entire diameter of the reactor cross-section, so that it is ensured that the gasification agent is distributed with the uniformity required for the development and maintaining of a fluidized bed.

Figs. 3a to 3c are transverse cross-sectional views through various alternative embodiments of distribution device, these distribution devices being essentially designed such that particles of solid material coming from above cannot be deposited thereon. The distribution devices each having sloping surfaces 42 which form a roof-like apex which deflects solid material to the sides of the device i.e.

maintains a throughflow through the reactor. The distribution devices 40 also have a cavity 41 extending axiallytherethrough, laterally extending outlet bores interconnecting cavity 41, with outletaper- tures 46. The outlet bores can be arranged horizontally but this is only in exceptional cases. Normally the outlet bores will generally be directed more or less downwardly. In the case of distribution devices which taper at the bottom, the outlet bore or bores can be directed perpendicularly downwardly, the outlet aperture 46 opening at the base apex of the cross-section (see Fig. 3c).

Claims (8)

1. A reactor for the gasification of solid carbonaceous materials in a fluidized bed under elevated temperature and pressure conditions, comprising a feed device for hot gasification agent, which device takes the form of an elongate conduit which is mounted in a reactor chamber, across said chamber, at least the top portion of the device when viewed in transverse cross-section, being formed by convergent surfaces which form an upwardly directed apex, a cavity for said hot gasification agent, extending axially through said device, said cavity being connected with downwardly directed gas outlet apertures provided as spaced apart locations in said device.

2. A reactor as claimed in claim 1, in which the distribution device is arranged so as to extend along a diameter of the cross section of the reactor.

3. A reactor as claimed in any one of the preceding claims, in which two distribution devices are arranged in the same plane and are combined to form a cruciform fitting.

4. A reactor as claimed in any one of the preceding claims, in which at least one distribution device is arranged in the region of the transition between a lower, downwardly conically tapering portion of the reactor and a cylindrical portion of the reactor located thereabove.

5. A reactor as claimed in any one of the preceding claims, in which two or more distribution devices are arranged at different vertical positions in the reactor chamber.

6. A reactor as claimed in any one of the preceding claims, in which the outlet apertures are staggered relative to one another in the longitudinal direction of the distribution device on opposite sides thereof.

7. A reactor as claimed in any one of the preceding claims, in which the or each distribution device is made from a ceramic.

8. A reactor for the gasification of solid carbonaceous materials on a fluidized bed under elevated temperature and pressure conditions, constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.