Pyrolysis reactor

A device for pyrolysing biomass comprises: a reactor space; a first feed for biomass material connecting to the upper zone thereof; a second feed for heated heat carrier material connecting to the upper side of the reactor space; a first discharge for pyrolysis gas connecting to the upper zone of the reactor space at a distance from the first feed; and a second discharge for solid material, for instance carbon and heat carrier material, connecting to the underside of the reactor space. A substantial separation between the discharge flows of pyrolysis gas and solid material takes place predominantly under the influence of gravitational force, without interposing of a cyclone. The reactor space is modeled such that the direct flow from the first feed and the second feed to the first discharge is blocked. A mechanical mixer is present in the reactor space for the purpose of mixing the flow of biomass material with the flow of preheated heat carrier material.

BACKGROUND OF THE INVENTION

The invention relates to a device for subjecting biomass to pyrolysis, which device comprises:

a reactor with a housing and a reactor space present therein;

a first feed for biomass material or other organic material connecting to the upper zone of this reactor space;

a second feed for heated heat carrier material, for instance sand, connecting to the upper side of this reactor space;

a first discharge for pyrolysis gas connecting to the upper zone of this reactor space at a distance from the first feed; and

a second discharge for solid material, for instance carbon and heat carrier material, connecting to the underside of this reactor space.

Such a reactor is known in many embodiments from, among others, WO-A-03/106590, WO-A-2007/017005 and DE-A-197 38 106.

Pyrolysis gas already occurs in the reactor space in the region of the mixer. This gas entrains fine carbon particles. The undesirable phenomenon may hereby occur that these fine particles accumulate in a separating cyclone forming part of the device, and cause blockage thereof after a period of time.

It is an object of the invention to solve this problem.

SUMMARY OF THE INVENTION

In this respect the invention provides a device of the above described type which has the feature that the reactor space is modelled such that the direct flow from the first feed and the second feed to the first discharge is blocked;

a mechanical mixer is present in the reactor space for the purpose of mixing the incoming flow of biomass material with the incoming flow of preheated heat carrier material; and

the maximum average velocity of the gas and the thereby entrained material in the reactor space downstream of the mixer at a temperature in the range of about 400° C.-550° C. is about as great as the terminal falling velocity, such that at least a substantial separation between the discharge flows of respectively pyrolysis gas and solid material takes place predominantly, and in any case for more than 50%, under the influence of gravitational force, in particular without interposing of a cyclone.

These measures according to the invention can effectively prevent any clogging and blocking occurring, despite the carbon and other solid material being of a somewhat tacky nature.

The structure according to the invention is able to wholly prevent the described undesirable phenomenon of the prior art. Carbon and, depending on the composition of the biomass, sometimes non-converted fibres and heat carrier material is discharged according to the invention substantially only via the second discharge, and the first discharge discharges substantially only pyrolysis gas.

Other than in the prior art, a direct flow, to be considered a short-cut flow, from the first feed and the second feed to the first discharge is effectively prevented according to the invention.

According to the invention substantially all solid particles are separated from the pyrolysis gas in the first part of the reactor where the mechanical mixer is situated.

The described separation can be effected in diverse ways. The reactor can for instance consist of two sub-spaces, i.e. the actual reactor space in which the mixer is situated, and a discharge part which connects on the underside to the lower part of said first sub-space and which connects on the upper side to the first discharge.

The velocity can for instance be set such that v<10 m/s, preferably v<5 m/s, more preferably v<2 m/s, and for a practically complete separation v<1 m/s.

In another embodiment the device has the special feature that an at least more or less vertical baffle is situated in the reactor space which connects to the upper wall of the reactor space, whereby the flow from the mixer, comprising a mixture of pyrolysis gas and solid material, and/or the part-flows of pyrolysis gas and solid material can only reach respectively the first discharge and the second discharge by passing over the lower edge of the baffle.

The reactor is preferably embodied such that the lower zone of the reactor space has a form narrowing toward the second discharge.

Functionally corresponding components are designated in all the figures with the same reference numerals. The design and relation to other components may differ in the different embodiments.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1shows a device1for subjecting a flow of biomass material or other organic material5to pyrolysis. The device comprises a reactor6with a housing7and a reactor space8present therein, a first feed10for a flow of biomass material5connecting to the upper zone9of this reactor space8, a second feed11for preheated heat carrier material12connecting to the upper part9of this reactor space8, a discharge13for pyrolysis gas14connecting to upper zone9of reactor space8, this discharge13being in the shown manner a substantial distance from first and second feeds10,11, in addition to a second discharge16for a flow of solid material17, such as carbon, possibly remaining fibres and heat carrier material, connecting to lower zone15of reactor space8.

The separation between the discharge flows of pyrolysis gas14and solid material17takes place substantially only under the influence of gravitational force, since the average velocity of the gas and the solid material entrained thereby has a low value, for instance 5 m/s, downstream of mixer18. By way of comparison: a cyclone generates flow speeds in the order of 20 m/s and more. Otherwise than a known pyrolysis reactor, device1does not comprise a cyclone.

Reactor space8is modelled such that the direct flow from first feed10and second feed11to first discharge13is blocked, so that no “short-cut flow” can occur. The flows14and17in reactor space8are indicated with arrows. It will be apparent that these arrows serve only by way of orientation, and that the actual flows have a more complex character.

Present in reactor space8is a mechanical mixer18, the schematically drawn blades of which are driven rotatingly by a motor (not shown). The mixer serves to mix the flow of biomass material5with heated heat carrier material12such as sand.

Situated in reactor space8is a vertical baffle19which connects against upper wall20of reactor space8.

The lower zone15of reactor space8has a form narrowing toward second discharge16. Side walls21,22of this narrowing part have an angle to the vertical of less than 30°.

FIG. 2shows a reactor2with a construction differing from that ofFIG. 1in the sense that baffle19has a greater vertical dimension but is still roughly the same distance from wall23located thereunder (this wall23having an inclining position in this embodiment) as from the horizontally placed wall23in the embodiment ofFIG. 1.

FIG. 3shows a device3in which a central peripheral baffle19connects to upper wall20. Situated on the underside of mixer space24is a horizontal deflecting battle25which deflects flows14,17laterally in the shown manner such that the flow of pyrolysis gas14undergoes a certain change in direction and can thus be more easily discharged to the two first discharges13.

FIG. 4shows a reactor4which differs from reactor3ofFIG. 3in the sense that the horizontal deflecting battle25is replaced by a roughly cone-shaped deflecting body26which makes it easy for the flow of solid material17to be guided downward in the direction of second discharge16.