SOLID BIOMASS MATERIALS

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates generally to processes involving flow of a particulate solid biomass material, and more particularly to a method for improving the flow properties of particulate solid biomass materials,

2. Description of the Related Art

[0002] There is a high level of interest in processes for converting solid biomass material to gaseous and/or liquid products, in particular gaseous and/or liquid fuel materials. Many of the proposed processes for biomass conversion require the solid biomass material to be provided in a small particle size, for example particle sizes rangiag from a few μm to several era, in many cases from a few μm to several mm.

[0003] Solid biomass particles in these particle sisεe ranges are prone to agglomeration, and even caking. TMs propensity makes it difficult to transport these particles by pneumatic conveyance. For this reason many prior art processes rely on screw feeders for transporting particulate solid biomass materials and for injecting such materials into conversion reactors.

[0004] It has been found, however, that the propensity of solid particulate biomass materials to agglomerate and/or cake causes variability in the mass feed flow of these materials, even when a screw feeder is used. This variability causes serious imbalances in the conversion reactions, in particular in reaction systems characterized by a short contact time, such as flash pyrolysis.

[0005] Also the feed into a screw feeder may be affected by this agglomeration and/or caking propensity, for example due to stalling or bridging of solid particulate biomass material in a hopper or other gravity-feeding device used to feed the screw feeder,

[0006] Thus, there is a particular need for a method for Improving the flow properties of solid particulate biomass materials, in particular solid particulate biomass materials having a mean particle size in the range of from 5 μm to 50 mm. BRIEF SUMMARY OF THE INVENTION

[0007] The present invention addresses these problems by providing a method for improving the flow properties of a particulate solid bioraass material comprising the step of mixing the particulate solid htomass material with a particulate solid inorganic material,

[0008] Another aspect of the invention comprises a method for feeding particulate solid biomass material into a conversion reactor.

DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention is based OB the discovery that the flow properties of a mixture of a solid particulate biomass material and a particulate solid inorganic material are significantly better than axe the flow properties of the solid particulate biomass material by itself.

[0010] Accordingly, the present invention provides a method for improving the flow properties of a particulate solid MoBiass materia! comprising the step of mixing the particulate solid biomass material with a particulate solid inorganic material.

[0011] The method Is particularly suitable for use with solid biomass materials comprising cellulose, such ss Hgnocellulosic biomass materials,

[0012] The particulate solid morgamc material may be water-soluble or water-insoluble. Water -insoluble particulate Inorganic materials are preferred.

[0013] In one embodiment, the particulate inorganic material is an inert material, that is, it does not catalyze conversion reactions of the biomass material. Suitable examples of inert materials include sand, quartz, silica, and the like.

[0014] The method may be used in conjunction with a catalytic biomass conversion process. For this embodiment, the particulate solid biomass material may be a catalytic material, that is, a material that catalyzes conversion reactions of the biomass materials. Suitable materials include solid adds, in particular zeolites, such as zeolite Y and ZSM-S, and zeolite containing materials, such as E-cat (the term used for "equilibrium FCC catalyst"); amphoteric materials, in particular aluminas; and solid bases, such as hydrotaJcite; hydrotalelte-ϊike materials; anionic clays; cationic clays; layered hydroxy metal salts; zeolites; water-insoluble earth alkaline metal salts; mixed metaJ oxides; and mixtures thereof. [0015] In one embodiment the solid biomass material is impregnated with from 0.1 wt% to 6 wt% of a water-soluble inorganic material. Examples of suitable water-soluble inorganic materials include the salts, oxides and hydroxides of the alkali metals and the earth alkaline metals.

[0016] In general, the solid biomass material should not be heated to temperatures above

250º C while being mixed with the solid inorganic material, in particular when the solid inorganic materia! has catalytic properties, to avoid premature conversion of the biomass material. Preferred are mixing temperatures below 125 °C.

[0017] The mixing ratio of particulate inorganic material/solid particulate biomass materia] should be high enough for the inorganic material to impart its positive effect on the flow properties of the resulting mixture, in general, the desired minimum mixing ratio is 0.1:1, a mixing ratio of at least 0.5:1 being preferred. Technically there ϊa no upper limit to this ratio, as mixtures containing large amounts of inorganic particulate materials have excellent flow properties. For economic reasons it is desirable not to exceed mixing ratios greater than 10: 1. Preferred is an upper limit of 5: 1. Preferred are mixing ratios in the range of from 1.5:1 to 3.5:1.

[0018] The desired particle size of the particulate solid biomass material is to a large extent determined by the reactor type used for the subsequent conversion reaction. If the biomass materia! is intended to be converted in a fluidized bed or a transported fluid bed, the preferred average particle size is in the range of from 5 μrø Io 50 mm, preferably from 70 μm to 5 mm, more preferably from 100 μm to 1000 μm.

[0019] Having a greater density, the particulate solid inorganic material preferably has a smaller particle size in order to be readily fhπdizable in a subsequent fhύdizcd bed of a conversion reactor under the same fluidization conditions.

Preferred average particle sizes of the particulate solid inorganic material are in the range of from 40 μm to 200 μm, preferably from 50 μm to 80 μm.

[0020] The particulate inorganic solid materia! has a shape index in fee range of from 2 to 1, preferably from 1.5 to 1 , That is, preferred are inorganic particles having a spherical shape or approaching a spherical shape. Preferred also are inorganic particles having a greater hardness than do the solid biomass particles. This is expressed in the attrition index of the particles. The inorganic particles preferably have a lower attrition index than do the solid bioroass particles. Upon mixing of the solid biomass particles and the inorganic particles, for example during pneumatic conveyance, interaction between the two types of particles can reduce the particle size of the solid biomass particles.

[0021] The method of the invention is particularly useful for conveying solid particulate biomass material by a screw feeder system, or pneumatic conveyance, or for fluidizing such material, in preparation to conducting a conversion reaction with the biomass material.

[0022] Thus, in one embodiment of the invention, the method comprises the additional step of feeding the mixture of particulate solid biomass material and particulate solid inorganic material into a pyrolysis reactor. In a preferred embodiment the pyrolysis reactor is a fluidized bed reactor.

[0023] In an alternate embodiment the pyrolysis reactor is a fluid transport reactor. [0024] In yet another embodiment the pyrolysis reactor is a cyclone reactor.

The following example is provided to further illustrate this invention and is not to be considered as unduly limiting the scope of this invention.

EXAMPLE

[0025] Wood particles with an average particle size below 140 microns were charged to an upflow pyrolysis reactor using a screw feeder system. The following Tables 1 and 2 include time measurement data (including line out period, material balance period, total time on stream, and the time on stream per six hour day) for runs with wood only (Table I ), and runs with a mixture of 60% catalyst and 40% wood being charged to fee screw feeder,

[0026] As can be seen from the data in the Tables 1 and 2 above, the runs wherein only wood was feed through the screw feeder to the reactor, the total on stream periods ranged from just 30 to 49 minutes, whereas, for the runs including the 40/60 catalyst to biomass mix the total time on stream periods ranged from 90 to 360 minutes. Also, the reactor never did line out for the runs including only wood as the feed. This data demonstrates the advantages of the inventive process of mixing biomass particles with an inorganic solid material to improve the flow properties of the resulting mix over that for biomass alone.

[0027] Thus, the invention has been described by reference to certain embodiments discussed above, It will be recognized that these embodiments are susceptible to various modifications and alternative forms well known to those of skill m the art

[0028] Many modifications in addition to those described above maybe made to the methods and techniques described herein without departing from the spirit and scope of the Invention. Accordingly, although specific embodiments have been described, these are examples only and are not limiting upon the scope of the invention.