GB2514312A - Filter and process for producing liquid products from biomass pyrolysis products - Google Patents

Abstract

A porous elongate filter unit for filtering particular matter from a gaseous and/or vapour mixture as obtainable during the pyrolysis of a carbonaceous feedstock, comprises: a first layer 5 of a porous, gas permeable filter medium having an average pore size in the range of from 1μm to 250 μm and a second layer 7 of a porous, gas permeable material having an average pore size in the range of from 1 μm to 250 μm. The second layer being positioned in a downstream direction of the gas flow with respect to the first layer. Optionally, at least one support layer 6, 8 structurally supports the first and/or the second layer. Preferably the filter medium is a ceramic, silica or metal that can withstand temperatures of up to 10000C. Advantageously the filter unit provides an improvement in the product oil of processes such as the pyrolysis of vegetable oils, algal biomass, wood and such like.

Description

FILTER AND PROCESS FOR PRODUCING LIQUID PRODUCTS FROM

BIOMASS PYROLYSIS PRODUCTS

TECHNICAL FIELD OF THE INVENTION

The present invention relates to a process of producing liquid products from carbonaceous feedstock, such as biomass through fast pyrolysis, further also comprising the catalytic processing of a pyrolysis oil in the gas/vapour/aerosol phase, and the use of the pyrolysis oil.

BACKGROUND OF THE INVENTION

ic The use of renewable energy sources is becoming increasingly important as a feedstock for production of liquids and/or hydrocarbon compounds. In particular biomass derived from plants and municipal waste is increasingly considered valuable sources for liquid and gaseous hydrocarbon compounds.

One of the existing processes for the conversion of biomass includes the steps of pyrolysing biomass to obtain pyrolysis liquids. This is a known process for converting biomass to a gas/vapour/aerosol stream, and the biomass might for example be straw, bagasse, or other agricultural wastes, waste paper, wood, or the organic fraction of municipal solid waste, the resultant gas/vapour stream is then subsequently cooled and pyrolysis liquids recovered by a variety of methods. The process may be applied to biomass grown specifically for the purpose, or to waste materials, such as waste wood and straw, however it is not limited to these materials. The pyrolysis process typically involves heating the biomass to an elevated temperature, possibly in the presence of a restricted quantity of air, typically less than 0.2 of stoichiometric ratio, to break down organic materials and to generate permanent gases such as carbon dioxide, methane, carbon monoxide, hydrogen and small quantities of ethane, ethane, propene, propane and other higher hydrocarbons, pyrolysis oil, and by-products such as char or charcoal, particulate carbon and pyrolytic water. The obtained pyrolysis gaseous mixture may be combustible, subject to the amount of inert gas present in the mixture and other factors such as stoichiometric air/fuel ratio, temperature, degree of mixing and/or use of additional combustible fuels. The condensable pyrolysis oil may be processed and/or upgraded to obtain specific chemicals, s groups of chemicals, non-fuel and fuel products.

Examples for such processes are disclosed for instance in W02008005476, disclosing a system comprised of dryer, pyrolysis reactor, char and thermal carriers separator, condenser and char burner for the production of energy, chemical products and other materials; US2010209965, disclosing a process for the thermal conversion of particle carbonaceous material as a source of energy into a particular fine particulate biomass is described; W02008092557, disclosing a process and a plant for the conversion of rape seeds and/or their derivatives, and W020091 38757, disclosing a process for the pyrolysis and gasification of biomass, using a mixing step involving a heat transmitter and transport by a system of screws.

Pyrolysis oils obtained typically comprise of a mixture of oxygenated compounds and water generated during the process and from the initial moisture content of the biomass. The process typically includes the cooling and quenching of the gaseous phase directly obtained in the pyrolysis reactor to separate off the formed pyrolysis oxygenated compounds, hydrocarbons and water from non-condensable [at room temperature] gaseous compounds.

Further liquids recovery may be performed using coalescing filters, electrostatic precipitators, demisters and/or a combination of these and other physical recovery methods.

In classical crude oil gasification plants, purification of the gases is typically achieved by using hot gas filters consisting of several hollow ceramic filter candles hanging from a top plate, whereby the gas stream flows through the filter candles, allowing cleaning of the candles to remove accumulated solids by back pulsing.

In the biomass pyrolysis process, though, a problem encountered upon cooling is that char and large organic molecules formed during the process, can form a sticky layer and clog the pores of the ceramic filters used, leading to a pressure drop increase across the filter over time. Ceramic filters are comprised of, but not limited to: silica/alumina, calcium silicate with mineral s fibres, e.g. Cao, MgO and lesser oxides, glass fibre based media and other porous, woven and/or meshed and/or fibrous substrate.

Some of the compounds used in the filter can cause pyrolysis gases and vapours to decompose, leading to pore blockage, surface fouling and a reduction in filtration performance, usually seen as an irreversible increase in ao pressure drop across the filter media.

Some of the larger molecules in the gas phase can also deposit on the surface or in the pores, leading to blockages and increased pressure drop across the candle. As a result, only few processes are reported to have operated in a continuous manner for shod periods of time without unscheduled interruptions necessitated by pressure build-up and fouling, while increasing the risk of cracks or broken filter candles upon back pulsing and continuing increase in pressure drop.

The formation of a char layer on a filter medium may be overcome by using a cyclone separator. In the cyclone, centrifugal force created by the swirling action separates the denser solids from the lower-density gases. The amount of centrifugal force generated is proportional to the square of the tangential entering velocity of the gas and solid mixture, as well as the inverse of the diameter of the cyclone. As the efficiency of separation of the solids from the gas is a function of the diameter of the solids, smaller particles are getting more difficult to separate and collect, hence reducing the ability of a cyclone to remove smaller particles and droplets from gases. This is more pronounced when a cyclone is scaled up in size, and/or where the particle size decreases, especially below 10 pm. As a result, the thus obtained pyrolysis liquids tend to comprise unacceptably high levels of metals and ash, making them unsuitable for use as a fuel and for direct upgrading treatment to hydrocarbons, though this does not necessarily preclude their use in other applications, e.g. product or chemical synthesis not related to energy applications To counter the loss in efficiency, often higher gas velocities are s employed. This however results in a higher pressure drop and can lead to increased erosion of the reactor and cyclone vessel, necessitating the use of more durable, and hence expensive materials, and in some cases, wear plates or parallel unit operations. Similar devices which work on the basis of density difference include dropout pots, rotary particle separators and baffle plates in vessels.

Accordingly, it would be highly desirable have a process that can be operated on a continuous basis, and without the need to resort to measures such as cyclones separation technology, making the process more efficient in terms of energy and materials used. It would furthermore be highly desirable to produce pyrolysis products of higher purity, in terms of low dissolved inorganic elements and compounds and solid content, which may be subjected to further treatment or upgrading steps without the need for extensive pre-processing or treatment to reduce the inorganic component content and solids.

Yet further, liquid phase filtration of pyrolysis oils to remove solids has proved very problematical. The presence of solid particles in the liquids appears to cause the pyrolytic lignin present in the liquids to nucleate around the char particles, inhibiting filtration and causing excessive pressure build-up across the filter media.

The addition of a co-solvent such as an alcohol is typically required to improve filtration, by reducing the viscosity and solubilising the pyrolytic lignin, however this is generally not desirous as the alcohol cannot be easily recovered after filtration of the liquid. Liquids derived from forestry residues, which may have multiple phases, or globules present in or on the liquid, exhibit additional challenges with a low polarity, lower density phase which is only partially soluble in alcohols and is more soluble in hydrocarbons thereby requiring the application of two or more solvents to ensure effective filtration.

Hence, while some processes are available to remove solids from the vapours, there is a need for an improvement in the processes for filtration of pyrolysis gases and vapours to useful liquid products.

SUMMARY OF THE INVENTION

Accordingly, in a first aspect, the present invention relates to a porous elongate filter unit for filtering particular matter from a gaseous and/or vapour mixture as obtainable during the pyrolysis of biomass, comprising: (i) a first layer of a porous, gas permeable filter medium having an average pore size in the range of 1 pm to 250 pm; (H) a second layer of a porous, gas permeable material having an average pore size in the range of from 1 pm to 250 pm, the layer being positioned in a downstream direction of the gas flow with respect to the first layer; and (Hi) optionally, at least one support layer structurally supporting the first and/or the second layer.

In a second aspect, the subject invention relates to a process for the preparation of filtered gaseous pyrolysis products comprising: (a) providing carbonaceous material to a pyrolysis reactor; (b) heating the carbonaceous material in the pyrolysis reactor under pyrolysis conditions to effect pyrolysis of the material into a gaseous and vapour/aerosol state in a substantially oxygen free and pressure controlled environment; (c) passing the gases through one or more filter units as set out herein above, to obtain separated-out particulate matter, and a purified gaseous pyrolysis mixture.

The separated-out particulate matter is herein referred to as char, and includes ash and carbon products such as carbon and tar formed in the process.

Preferably the process further comprises a step (d), of condensing normally liquid products from the purified gaseous mixture, to obtain normally liquid pyrolysis oil.

In a further aspect, the subject invention relates to an apparatus for biomass pyrolysis, comprising at least one filter unit according to the invention.

s The present invention further also relates to a process for pyrolysis of biomass, comprising the steps of (e) subjecting a feed comprising a pyrolysis oil to an esterification process, or a further reaction step, which may include, but is not limited to hydropyrolysis, hydrodeoxygenation and/or deoxygenation step in the presence of a catalyst comprising an active component on a ao catalyst carrier that is inert at the reaction conditions, to obtain a product stream comprising a partially deoxygenated pyrolysis oil to obtain a partially deoxygenated pyrolysis oil having an oxygen content of 10 to 30 wt% [dry liquid basis], and (f) separating at least one product fraction from the product stream obtained in (g), wherein the pyrolysis oil is obtained directly from i pyrolysis of biomass under suitable conditions, and the filtration of the thus obtained gaseous and fluid product through a filter according to the invention described herein prior to condensation and recovery of the normally fluid products.

The present process further preferably comprises the step of (h) blending the pyrolyis oil obtained in (d) and/or at least one product fraction obtained in (g) with at least another fuel compound and/or an additive to obtain a biofuel suitable for use as is, or as intermediate following further processing to a hydrocarbon fuel or blendable component.

Furthermore, as an alternative approach, the present invention also relates to a process wherein the hydrogenation step is carried out in the presence of a hydrocarbon feed derived from a mineral crude oil or other suitable hydrogen carrier and/or donor material, directly resulting in an upgraded fuel product comprising biofuel components.

The hydrocarbon products include aliphatic, aromatic and cyclic hydrocarbon compounds which can directly be used, or when treated further can be converted into fuels.

Brief Description of the Figures

These and further features can be gathered from the claims, description and drawings and the individual features, both alone and in the s form of sub-combinations, can be realized in an embodiment of the invention and in other fields and can represent advantageous, independently protectable constructions for which protection is hereby claimed.

Embodiments of the invention are described in greater detail hereinafter relative to the drawings, wherein: Fig. 1 discloses a schematic diagram of an exemplary filter according to the invention.

Fig. 2 discloses a cross-cut of the filter unit.

Fig. 3 discloses a top view of the filter unit.

Fig. 4 discloses a schematic view of a preferred filter unit according to the invention in a filter chamber/housing.

Fig. 5 discloses the schematic view of a further preferred filter unit according to the invention in a filter chamber/housing.

Detailed Description of the Invention

The term "average pore size" is to be understood as determined in accordance with ISO 565 (1987). The term "porosity index" P1 is to be understood as Fl = 1OO*(1d) wherein d = (weight of 1 m3 porous filter material/ specific weight per 1 m3 of the substance out of which the porous material is provided).

In preferred embodiments, the filter medium preferably has a porosity index of 45% to 95%, such as for example 50% to 90%, 65 to 85%.

The filter medium preferably is inert under reaction/filtration conditions, i.e. it does not react or physically deform under the temperature and in the presence of pyrolysis mixture and other gases. Suitable materials include ceramic materials, silica, and metals or metal alloys. Metals and/or metal alloys are particularly advantageous due to the inherent lower acidity as compared to ceramics, their resistance to water and corrosion resistance.

Preferred materials include silica, copper, platinum, palladium; stainless steel alloys, nickel, Inconel, or a combination of these and similar materials that can withstand temperatures of up to 1000°C, and gas velocities s and compositions as typically present in pyrolysis gas. Combinations of metals and ceramics, e.g. metal coated ceramics, and/or ceramic coated metals compositions may also suitably be employed.

Preferably, the filter medium comprises one or more mesh structures formed from fibres or wires, but may also include sintered materials giving similar performance and robustness. Applicants found that when employing a filter unit according to the invention, filter cakes built up to only a small depth, and regularly fell off into the space below the filter unit, requiring no back-pulsing or any mechanical attempt to remove particulate filter cakes formed on the filter units during continuous operation for several hours until effectively the biomass fuel foreseen of the experiments ran out, or runs were ended under controlled and planned conditions.

The filter medium may comprise wires, fibres or expanded plates, in particular for the filter medium with the larger pore size. These may be prepared from metals or alloys, from silica or ceramics, or any other suitable material that is essentially inert at the reaction conditions.

Alternatively or additionally, the filter medium may comprise metal powder sheets, perforated sheets such as perforated metal, silicon or ceramic sheets or expanded metal, silicon or ceramic sheets.

The figures depict preferred embodiments of the filter unit and the filter unit in its housing (see following reference table): Reference Table for Figures ________________ ________________ Feature Reference Feature Reference 1 Filter Unit 13 Inlet from Pyrolysis Reactor 2 Base Plate 14 Upstream Pressure Tapping 3 Access Flange 15 Filter Housing Wall 4 Cut-out 16 Heating Element First Filtration 17 Adjustable medium, e.g. moveable Sleeve Perforated Plate 6 Coarse Support 18 Char Drop Mesh Out/Collection Zone 7 Second Filtration 19 Insulation Medium, e.g. fine mesh 8 Outer Support 20 Heating Element 9 Outlet to Quench 21 Inlet from Column Pyrolysis Reactor Filter Housing 22 Downstream Temperature Measurement 11 Downstream 23 Downstream Temperature Pressure Tapping Measurement 12 Outlet to Quench Column The term "metal fibre" and/or "metal wire" is to be understood as a fibre made of any suitable metal or metal alloy. Metal fibres or wires may be prepared by different suitable production processes such as (bundle) drawing processes, coil shaving processes, electro-deposition, and/or or melt s extraction. Metal fibres are typically characterised by an equivalent diameter, for the invention preferably in the range of 1 pm to 1 mm. The fibres may be long filaments, or may be provided as fibres having an average length in the range of 1 mm to 1000 m.

Metal fibres or wires may advantageously be present as metal wire mesh or grid. Also any support structure may advantageously be formed such material to reinforce the filter medium. Metal wires may be present as metal wire mesh or grid. Alternatively or additionally, the filter medium may comprise metal powder sheets, perforated sheets such as perforated synthetic sheets or expanded synthetic sheets. Less commonly employed, yet also suitable may be porous layer of particles with the required pore size as obtained through sintering of metal powders.

The term "filter medium" is to be understood any medium, which is able to separate solid particles from a fluid, more specifically from a gaseous feed stream.

In a preferred embodiment, the filter medium comprises a woven or knitted filter medium. In a different preferred embodiment, the filter medium comprises a sintered material. In yet a further preferred embodiment, the filter medium comprises of a sheet-like material with elongate or otherwise dimensioned and formed perforations, e.g. meshes, grids, expanded sheets or the like. Combinations of woven or knitted filter mesh, sintered and/or sheet like materials such as grids or expanded sheets may also be preferably employed.

The term "ring shape" is to be understood as having a shape with an outer edge and an inner edge which inner edge encompasses the centre of the outer edge and which inner edge is usually concentric with the outer edge, although the inner and/or outer edge is not necessarily circular. Circular edges are however preferred.

The term "elongate" refers to a filter having a shape wherein the length of the filter is higher than its width.

s The terms "substantially rectangular", "substantially conical" and "substantially cylindrical" are to be understood as allowing deviation from a perfect rectangular, conical or cylindrical shape due, for example, to normal production tolerances, or as required by the purpose or shape of the filter location, with angular deviations or deviation on length dimensions as appropriate.

The term "lumen" relates to space enclosed by the gas permeable filter medium. The lumen is fluidly connected to a further downstream part of the apparatus.

In the filter unit according to the invention, layer (i) preferably envelops layer (H).

The gas permeable and porous filter medium preferably comprises a woven or non-woven sheet like material, more preferably at least one mesh or grid-like material.

The actual shape of the filter unit was considered as less relevant, as experimental results showed with different cone -or cylinder shaped filter unit showed. Accordingly, the filter unit may have any suitable shape or dimension, preferably a pyramidal, cylindrical, frustro-conical or conical shape.

For practical reasons, the filter unit according to the invention is a so-called filter candle. It thus preferably further comprises an axial opening, and an end fitting fixed to the filter medium, the end fitting providing a first end of the filter unit, the end fitting having an end inner surface defining an end fitting opening through the end fitting, the end fitting opening being co-axial with the axial opening of the filter unit; wherein layer (ii) forms a first hollow lumen positioned within the axial opening of the filter unit.

The heat source required for the filter housing may involve a furnace or electrical heating means having an independent heating source not associated with another part of the process.

Alternatively, heat energy from other parts of the process may be reclaimed and/or recycled and used for heating of the filter and/or filter s housing. In a preferred form, the heat energy from heating means of one or more of the pyrolysis chambers is directed to the filter housing.

If for instance the pyrolysis reactor is heated by a furnace, the heat from the furnace exhaust gases may be reclaimed to e.g. preheat the feed material, using suitable heat exchangers, and then employed for maintaining ao the filter housing at a desired temperature range.

The present invention further advantageously relates to a process for the preparation of filtered gaseous pyrolysis products comprising: (a) providing carbonaceous material to a pyrolysis reactor; (b) heating the carbonaceous material in the pyrolysis reactor under pyrolysis conditions to effect pyrolysis of the material into a gaseous, vapour and/or aerosol state in a substantially oxygen free and pressure controlled environment; and (c) passing the gases through one or more filter units according to the invention, to obtain separated-out particulate matter, and a purified gaseous pyrolysis mixture.

In step (a), the carbonaceous feedstock is provided to the pyrolysis reactor. There are a number of different reactor configurations that can be employed, including ablative systems such as screw-pyrolysers, fluidised beds, stirred or moving beds and vacuum pyrolysis systems. Preferred is a fluidised bed reactor due to the possibility of a comparatively fast pyrolysis, and the fast removal of the formed products.

In a fluidised bed reactor, typically a pre-weighed mass of inert material, such as round sand is also present. The inert material and the feedstock are the typically fluidised by a gas, which may advantageously be an inert gas, recycled non-condensable pyralysis gases, partially combusted non-condensable pyrolysis gases, fully combusted non-condensable gases, combustion gases from another material or a combination of these.

The pyrolysis reactor is typically externally heated, while the heat provided to the fluidised bed leads to the pyrolysis of the introduced biomass.

s The reactor pressure preferably is in the range of from 0 to 50 bar g, but preferably in the range of from 0 to 12, more preferably in the range of from 0.1 to 1, yet more preferably less than 0.2 bar g.

The pyrolysis products exit the reactor and preferably pass directly into the hot vapour filter vessel or housing where the gases, aerosols and vapours pass through the filter substrate, while and char particles are essentially stopped by the filter media.

The filtered vapours are then cooled and condensed, preferably comprising a quenching step. An example for such a quenching step involves cooled recirculated isopar V, for instance in a co-current weir-tray column. The co-current flow advantageously reduces fouling and the majority of the pyrolysis vapours and condensable organics can be recovered in such a column.

The cooled non-condensed gases, typically also comprising thermally stable aerosols, will disengage from the condensing liquids, and are preferably passed into a further separator unit to remove aerosols. This may be any suitable separation unit, but preferably involves electrostatic precipitation, e.g. with a wet-walled electrostatic precipitator where the charged central electrode imparts a charge on the generally upflowing aerosols, which essentially deposit on the earthed wetted wall, to obtain deposited aerosols, and a residual cleaned syngas feed.

The residual cleaned gases may then preferably subjected to a further condensing step to remove residual water and traces of low boiling compounds such as e.g. acetic acid, prior to atmospheric discharge or recycling to any suitable stage of the process.

Char collected on the filter was found to periodically drop off and is preferably collected in the bottom of the filter vessel or housing, which may be advantageously be fitted with a char collection vessel that permits to remove char during the operation.

The overall gas/vapour product residence time in the filter unit is s preferably up to 4.2 s, and maintained at an average temperature in the range of from 460-485°C prior to quenching.

The pyrolysis reaction step (b) is typically characterised by high heating rates and short vapour residence times. Therefore, step (a) generally includes preparation of a suitable feedstock composition, e.g. suitable particle size and particle size distribution, appropriate moisture levels and dust load for any chosen reactor design and configuration.

In step (b), the biomass feedstock particles are typically pyrolysed at a temperature in the range 350°C to 650°C, i.e. lower than temperatures typically used for gasification.

Preferably the pyrolysis step (b) lasts for at least 1 second, more preferably at least 5 seconds, more preferably at least 10 seconds, and at most 30 seconds.

As the skilled person will appreciate, the preferred time for the pyrolysis step depends on the properties of the biomass particles, and in particular on the dimensions of the biomass particles, the ash and water contents. For example, the time for the pyrolysis step may be at least one minute. For smaller particles, the time for the pyrolysis step may be relatively shorter than the time for larger particles. Generally, the conditions for pyrolysis as described in WO 2010/130988, and the citations therein may be applied; preferably, however vapour temperature is such that neither water formed or present, nor the formed vapours condense prior to step (d).

The reactor is preferably operated at a temperature in the range of 400 to 700°C, more preferably from 450 to 570°C, yet more preferably from 500 to 520°C to maximise the yield of organic, condensable products.

so In the fluidised bed, the feedstock particles are heated by contact with the fluidised sand bed and to a lesser degree by the hot gas used to fluidise the sand bed. Char removal from the bed can be by entrainment in the pyrolysis products and gases, or by other means, e.g., solids overflow via a weir or via an internal cyclone to remove large particles from the exiting s products.

The pyrolysis reactor internal geometry is preferably chosen such that only fully reacted carbonaceous feed particles exit from the reactor, leaving new carbonaceous teed and partially reacted carbonaceous feed in the reactor.

The fluidised bed preferably operates at 1.1 to 4Umi, more preferably at from 2 to 3.5 Umf, wherein Umf is the minimum fluidising velocity of the fluidised bed. In step (c), the gases formed are passed through one or more filter units according to the invention, to obtain separated-out particulate matter, and a purified gaseous pyrolysis mixture. Also in this step, a vapour temperature should be maintained such that neither water formed or present, nor the formed vapours condense prior to step (d).

The temperature of the gas/vapour phase product obtained in step (b) is preferably in the range ot 350 to 650°C. Preterably, it is in the range ot 425 to 525°C, since the operation at a higher range would lead to a higher amount of permanent or non-condensable gas formation, and a reduction in yield of organics in the pyrolysis oil.

The process is preterably conducted such that the gas/vapour phase product residence time at the tilter unit is in the range of trom 1 second to 10 seconds, preferably of from 0.5 to 5 seconds.

The filtration or superficial gas velocity through the filter unit preferably is in excess ot 0.5 cm/s, with a preferred upper limit of 10 cm/s. Preferred is the range of from 2 to 5cm/s.

The absolute gas pressure in the filter unit may for example be in the range of 1 to 10 bar absolute gas pressure, such as for example ot from 1 to 5 bar absolute gas pressure, or of from 1.2 to 3 bar absolute gas pressure, although it is not necessarily limited to those ranges.

In step (d), the filtered pyrolysis gases are preferably condensed into normally liquid products. Normally gaseous products that are not condensed may advantageously be employed as fuel gas for the pyrolysis stage or other s processes within and external to the pyrolysis process.

The condenser means may include a selective condensation, or staged condensation to remove light fractions from the gaseous pyrolysis material as required.

The condenser means may differentially condense different fractions of the gaseous product to select one or more fractions suitable for use as a fuel, directly, or after subsequent catalytic treatment.

For example, the condenser means may include one or more condensers capable of condensing fractions at different temperatures or ranges thereof. In a preferred aspect, the condenser means includes a condenser for obtaining fractions suitable for treatment into lighter and heavier fractions. Typical condensing means include direct liquid quenching, staged differential temperature quenching and cooling, indirect cooling in heat exchangers, spray towers, distillation columns and/or direct contact with liquids in towers of various configurations.

In a further preferred aspect, the invention provides for a process for the thermal conversion of carbonaceous materials into fuels, wherein char and particulate matter is removed from pyrolysis gases by use of one or more of the filters according to the invention.

Accordingly, in a further preferred aspect, the invention provides for a process for the pyrolysis conversion of carbonaceous materials into fuel products, preferably in a continuous manner. The continuous process system may operate, in principle, similar to a batch system. It may have, however, several distinct refinements that differ from the batch system. Principally, the continuous process may include a continuous feed system to the pyrolysis chambers and/or distillation columns in lieu of one or a series of condensers.

The invention further preferably relates to a pyrolysis apparatus comprising: (a) a pyrolysis reactor chamber that heats and thermally decomposes a carbonaceous, preferably biomass material to generate a solid, called char and a particular matter containing pyrolysis gas and/or vapour and/or aerosol s from the carbonaceous biomass material, and (b) a filter comprising at least one filter unit as set out herein above, to essentially remove char and particular matter from a filtered gas and/or vapour stream, and (c) a condenser means for cooling and condensing at least one normally fluid pyrolysis oil fraction from the filtered gas and/or vapour stream, and optionally, (d) a hydropyrolysis, hydrodeoxygenation and/or deoxygenation unit for treatment of the normally fluid pyrolysis oil fraction.

The pyrolysis apparatus or process plant may be employed to convert carbonaceous matter, i.e. biomass materials and/or other suitable fees, such as the organic fraction of municipal solid waste, into useable clean fuel, in particular boiling in the middle distillate range. Suitable carbonaceous materials include biomass materials such as vegetable oils, algal biomass; animal debree such as chicken litter; lignocellulosic materials, such as wood chips, saw dust, waste paper, bagasse, grass, straw or corn husks, and/or any other suitable biomass materials that can be subjected to a pyrolysis process, and that generate normally liquid pyrolysis oils. Preferred due to availability are spruce wood, miscanthus, wheat and/or rice straw, willow, corn husks and chicken litter, and combinations thereof The term "normally" liquid refers to materials that are liquid under normal conditions, i.e. a temperature of 25°C and an absolute pressure of 1013 mbar.

Plant derived biomass is generally composed of three main groups of natural polymeric materials: cellulose, hemicellulose and lignin. Other typical components include smaller organic molecules or lower molecular weight polymers, and inorganic compounds such as metal salts and/or silica.

These are present in differing proportions in different biomass types, and thereby may influence the product distributions on pyrolysis. In particular alkali metal salts are known to catalytically promote pyrolysis reactions leading to increased cracking and hence gas make in some circumstances, in addition to ash yield.

s The process thermally degrades carbonaceous, preferably biomass materials in an essentially oxygen-free environment inside a pyrolysis chamber, thereby pyrolysing it into a gaseous state under the reaction conditions. The components referred to in the gaseous state comprise gaseous components, vapours and/or aerosols.

The hot pyrolysis gases are then directly passed through one or more filter units as described herein above, without the need for a removal of particulate matter and char by a cyclone.

Advantageously, this may also be done in conjunction with addition of reagents that may be added to the gas phase prior to, or after passing the filter, for instance in the filter of, but not limited to, alcohols having a low boiling point, e.g. methanol, ethanol or isopropanol, or other reactive gases such as hydrogen. In the case where there is the potential for the simultaneous removal of acid gases preferably addition of suitable additives, such as metal compounds, more preferably calcium compounds may advantageously be considered.

Additional loading of the pyrolysis vapour feed, or carbonaceous material with particulate matter or dust, which may increase the specific weight of a filter cake, and hence improve removal of the filter cake by increasing its density is undesired, since it inadvertently increases the amount of fines in the pyrolysis oil.

Accordingly, the filter according to the present invention is preferably not immersed in, or directly contacted by the fluidised bed for char removal, as for instance disclosed in E. Hoekstra at al, in "Fast Pyrolysis of Biomass in a Fluidized Bed Reactor: In Situ Filtering of the Vapours ", Ind. Eng. Chem. Res. so 2009, 48, 4744-4756, but spaced such that it is not directly impinged by the fluidised bed particles, and more preferably placed in a filter housing separate from the pyrolysis reactor vessel.

Preferably, the pyrolysis vapour feed is supplied directly and without an intermediate stage from the pyrolysis reactor to the filter.

s The apparatus further advantageously comprises means for applying a reverse flow, preferably as a back pulse. Although not required in the experiments that are described herein below, it should not be excluded that this may advantageously be done from time to time to remove the filter cake at least in pad during the operation. Alternative mechanical cleaning operations may also be employed.

Cleaning of the one or more filter elements is preferably performed individually, or serially during operation, by reversing the gas flow. This is preferably done with flue gas exhibiting the same, or even higher temperature than the vapours emanating from the pyrolysis process. This may be done through simple pulsing, jet pulsing, or under addition of suitable reagents, e.g. solvents, causing a backpulse due to evaporation and expansion.

The thus obtained liquid products were found far superior as both direct fuel oils, but also al feeds for further upgrading stages due to the strongly reduced char and metal contents. Accordingly, the present invention also relates to a normally liquid pyrolysis oil comprising less than 25 ppm of Calcium, less than 10 ppm of Potassium, less than 10 ppm of Magnesium, less than 27 ppm of Sodium, and/or less than 10 ppm of Aluminium.

Preferably, the liquid pyrolysis oil comprises less than 23 ppm of Calcium, more preferably less than 20 ppm, yet more preferably less than 15 ppm, such as 14, 13, 12, 11, 10,9, or less than 8 ppm (as determined by ICP-OES).

Preferably, the liquid pyrolysis oil comprises less than 9 ppm of potassium, more preferably less than 8 ppm, yet more preferably less than 7 ppm, such as 6, 5, 4, 3, 2, or less than 1.4 ppm.

so Preferably, the liquid pyrolysis oil comprises less than 9 ppm of Magnesium, more preferably less than 8 ppm, yet more preferably less than 7 ppm, such as 6, 5, 4, 3, 2, 1 or less than 0.6 ppm.

Preferably, the liquid pyrolysis oil comprises less than 23 ppm of Sodium, more preferably less than 20 ppm, yet more preferably less than 10 s ppm, such as 9, 8, 7, 6, 5, 4, 3, 2, 1, 0.5, 0.3, or less than 0.2 ppm.

Preferably, the liquid pyrolysis oil comprises less than 9 ppm of Aluminium, more preferably less than 8 ppm, yet more preferably less than 7 ppm, such as 6, 5, 4, or less than 3.4 ppm.

Preferably, the liquid pyrolysis oil comprises less than 5 ppm of Mn, more preferably less than 2 ppm, yet more preferably less than 1 ppm, such as 0.5, 0.4, or less than 0.3 ppm.

Preferably, the liquid pyrolysis oil comprises less than 40 ppm of Fe, more preferably less than 22 ppm, yet more preferably less than 8 ppm, such as 6, 5, 4, or less than 3 ppm.

Preferably, the liquid pyrolysis oil comprises less than 5 ppm of Ni, more preferably less than 4 ppm, such as 3, 2, 1, or less than 0.8 ppm.

Preferably, the liquid pyrolysis oil comprises less than 10 ppm of Cu, more preferably less than 3 ppm, such as 2, 1, or less than 0.1 ppm, or even essentially free of copper.

Preferably, the liquid pyrolysis oil comprises less than 21 ppm of Zn, more preferably less than 20 ppm, yet more preferably less than 11 ppm, such as 9, 8, 7, 6, 5,4, 3, 2, or less than 2 ppm.

The pyrolysis oils obtainable by the present process are furthermore highly storage stable without stabilisation or hydrotreatment, contrary to those typically obtained by processes that use cyclone separators, as also reported by e.g. Diebold, J.P. and Czernik, S, Energy and Fuels, 11, pp. 1081-1091.

The high stability not only makes the pyrolysis oils according to the invention particularly suitable as intermediate for a further upgrading, but also as direct fuels or fuel components.

The present invention therefore preferably also relates to a pyrolysis oil fraction obtainable by the subject process, having a storage stability as expressed by the increase of viscosity of an oil sample provided in a closed vessel maintained at 25°C over time, of less than 50% over a period of 30 days, more preferably less than 30% over a period of 30 days, and yet more s preferably less than 15% over a period of 30 days.

The viscosity increase preferably is less than 5 cst (mm2ls)I day, more preferably less than 3 cStlday, yet more preferably less than 1.5 cSt/day, again more preferably less than 1 cSt/day, and most preferably less than 0.5 cSt/day.

The viscosity referred to above is measured in a pyrolysis oil fraction containing 30 wt% of water as the kinematic viscosity at 40°C according to ASTM method D445A.

The thus obtained filtered pyrolysis gas and/or vapour mixture, optionally also comprising reagent additives, may then advantageously be fed into a hydropyrolysis, hydrodeoxygenation and/or deoxygenation unit, more advantageously, a catalytic hydrodeoxygenation unit, also referred to as a hydrogenation unit, typically by co-feeding a gaseous feed comprising hydrogen, to essentially to obtain water, a gaseous stream, and a normally liquid product stream of upgraded products.

In the catalytic hydrodeoxygenation unit, primarily the oxygen content of the pyrolysis products is reduced, thereby increasing the energy density of the thus treated products. Preferably, the catalyst particles present in the treatment unit are not prone to catalyst poisoning or consumption. In order to achieve this the thus obtained hydrotreated hot gases of the desired carbon length range may be condensed in one or more condensers or, more preferably, in one or more distillation towers, to yield a hydrocarbon distillate and water, and a gaseous fraction. The latter may advantageously be recycled to the process as a heat source.

In a hydropyrolysis unit, the pyrolysis oil is further subjected to a pyrolysis reaction in the presence of hydrogen. In a deoxygenation unit, the pyrolysis oil is subjected to a deoxygenation reaction, e.g. reforming, leading to essentially aromatic and unsaturated compounds. All of these reactions are preferably performed in the presence of suitable catalysts.

In a further preferred aspect, the invention provides for a process s wherein the catalyst particles comprise one or more active metal or metal oxide(s) on a carrier, more preferably selected from one or more of metals from Group VIII of the period system. Preferred catalysts comprise iron, cobalt, nickel, manganese, chromium, copper; alumina, silica/titanium oxide and/or mixtures thereof.

In a further preferred aspect, the invention provides for a substantially carbon based fuel product obtainable by the process of the invention.

Preferably, the fuel includes straight and branched chain aliphatic compounds, aliphatic compounds, branched and cyclic and aromatic hydrocarbons comprising of from 6 to 25 carbon atoms, more preferably from 12 to 18 carbon atoms.

The resulting mixture is preferably employed in admixture to other fuel components. Alternatively, the pyrolysis oil may be hydrodeoxygenated as co- feed with other hydrocarbon sources, such as crude mineral oil, tar sand-derived, or Fischer-Tropsch wax-derived hydrocarbon feeds. This has the benefit that a conventional reactor and catalyst may be employed without the need to specifically run the process under conditions where the water generated remains in the gaseous phase, and/or to control the overall need to avoid the presence of catalyst poisons.

The following, non-limiting examples illustrate the process according to the invention. It should be understood, however, that the invention is not limited to the specific details of the Examples.

Experimental Part Example 1: Pyrolysis test using a hot vapour filter (HVF) according to the invention Commercially available Lignocell BK 8/15 -Spruce with a particle size of from 1.4 to 1.8 mm, an ash content of 0.65 wt%, and a water content of 13.3 wt% on a dry basis was fed into a fluidised bed pyrolysis reactor containing a pre-weighed mass of round sand, which was fluidised by recycled non-condensable pyrolysis gases.

s The pyrolysis reactor was externally heated and the heat provided to the fluidised bed lead to the pyrolysis of the introduced biomass. The reactor internal geometry allowed only fully reacted biomass particles to exit from the reactor, leaving new biomass and partially reacted biomass in the reactor.

The biomass particles were heated by contact with the fluidised sand bed and the hot gas used to fluidise the sand bed at a temperature in the range of 400 to 70000, in particular at 500 to 520°C to maximise the yield of organic products. The reactor pressure was maintained at below 0.2 bar g.

The sand bed was operated at 2-3.5 Umf, where Umf is the minimum fluidising velocity of the sand bed.

The pyrolysis products exited the reactor and were passed into the hot vapour filter vessel where the gases, aerosols and vapours pass through the filter substrate and the char particles were stopped by the filter media.

The overall gas/vapour product residence was up to 4.2 s, at an average temperature 460-485°C prior to quenching.

Char collected on the filter periodically dropped off and was collected in the bottom of the filter vessel into a fitted char pot.

The filtered vapour were then cooled and quenched with cooled recirculated isopar V in a co-current weir-tray column. The overall gas/vapour product residence was up to 4.2 s, at an average temperature 460-485°C prior to quenching.

The cooled gases comprising residual aerosols were passed upwards into a wet-walled electrostatic precipitator to deposit upflowing aerosols on the wetted wall. The thus cleaned gases were passed through 2 dry ice/acetone condensers in series to remove residual water and traces of low boiling chemicals such as acetic acid, before being passed through a pre-dried and weighed cotton wool filter and a drying trap of dried molecular sieve of 3A pore size. The dried non-condensable gases were then passed through a gas meter prior to atmospheric discharge.

Four different filters according to the invention were employed, having s the following mesh sizes: 5, 25, 100 and 200 pm for the second filter, followed by a second mesh of 100pm Table 1 depicts the results of the different runs, as well as a comparative test run using a cyclone particle separator instead of the HVF.

Table 1: Overall Run Summary

Ex. 1 2 3 4 Comp.

Filter 100/25pm 100/lOOpm 100/Spm 200/lOOpm Cyclone, configuration __________ ____________ __________ ____________ no filter Feedstock 11.75 11.9 11.9 11.9 10.58 moisture, wt% __________ ___________ _________ ___________ _________ Ash, wt% (db) 0.65 0.65 0.65 0.65 0.65 Mass Balance __________ ___________ _________ ___________ _________ Char* 14.77 16.05 14.62 15.01 14.37 Organics* 49.12 47.26 49.10 44.32 52.15 Pyrol. Water* 12.66 13.87 11.23 11.97 10.47 Non 18.05 19.36 16.83 17.88 14.37 condensable gases __________ ____________ __________ ____________ _________ Closure 94.50 95.56 91.79 89.18 91.35 0 * [gflOOg db]; db = dry biomass; pyrolysis water excluding feedstock water.

The properties of the thus obtained pyrolysis oil fractions are depicted in Table 2: Table 2: Effects of HVF on pyrolysis oil properties. ___________ ________ Ex. 1 2 3 4 Comp.

Filter 100/25pm 100/lOOpm 100/5pm 200/lOOpm Cyclone, configuration __________ ____________ __________ ____________ no filter Oil Property* _________ ___________ _________ ___________ ________ Solids content 0.053 0.035 0.040 0.144 0.17 Lignin content 22.5 18.77 18.15 17.47 ND Moisture 28.76 31.73 27.49 30.93 24.48 * [gflOOg P0]; P0 = Pyrolysis Oil Additionally to the results in Tables 1 and 2, compared to the comparative example using a cyclone, a char reduction in the filtered HVF liquids of 74.3%, 69.0%, 78.8, 77.9% and 23.9%, respectively, was obtained.

Table 3 lists the composition of the obtained pyrolysis oils.

Table 3: Effects of HVF on pyrolysis oil property, such as organic elemental composition and metal contents of the oil ___________ _________ Ex. 1 2 3 4 Comp.

Filter 100125pm 100/lOOpm 100/Sum 200/lOOpm Cyclone, configuration __________ ____________ __________ ____________ no filter C, wt.% 42.45 37.95 39.53 36.84 41.64 H, wt.% 8.04 8.55 8.65 8.4 8.89 0, wt.% 48.93 49.31 48.3 52.62 49.02 N, wt.% 0.1 0.2 0.25 0.21 0.1 S, wt.% 0.1 0.1 0.1 0.1 0.1 Cl, wt.% 0.24 0.29 0.19 0.21 0.25 Ca, ppm 7.5 8.5 10.5 23 27 K, ppm 1.4 11.8 2.1 16 30 Mg, ppm 0.5 0.2 0.5 16 30 Na, ppm 0.1 25.3 20 27.9 22 Al, ppm 3.5 3.3 3.6 hA 17 B, ppm 38 22.6 17.9 7 7 Mn, ppm 1 0.3 0.2 0.2 5 Fe, ppm 21 7.4 2.5 3.7 41 Ni, ppm 3 1.6 0.7 0.6 5 Cu, ppm 2 Not Not Not 10 _____________ __________ detected detected detected _________ Zn, ppm 10 1.7 3.3 3.1 21 P,ppm 6 1.6 2.8 0.3 3 Compared to the comparative example using a cyclone, a reduction in metals of 64.71%, 76.47%, 82.35% 76.47% and 35.29%, respectively, was attained.

Table 4 finally lists the non-condensable gases formed during pyrolysis: Table 4: Effects of HVF on pyrolysis gas yield ___________ ________ Ex. 1 2 3 4 Comp.

Filter 100/25pm 100/100pm 10015pm 2001100pm Cyclone, configuration __________ ____________ __________ ____________ no filter Gas Yield, wt% (dry) _________ __________ _________ ___________ ________ H2 0.06 0.07 0.09 0.07 0.00 CO 7.25 7.46 6.67 6.90 5.72 CO2 8.94 9.83 8.35 8.92 7.04 CH4 0.89 1.03 0.84 1.02 0.73 C2H4 0.27 0.27 0.25 0.25 0.22 C2H5 0.30 0.28 0.28 0.32 0.26 C3H6 0.22 0.27 0.23 0.26 0.24 C3H8 0.12 0.15 0.13 0.15 0.16 n-C4H10 0.00 0.00 0.00 0.00 0.00 Total gas 18.05 19.36 16.83 17.88 14.36 yield __________ ___________ _________ ___________ _________ The results indicate that the filter and process according to the invention yield pyrolysis oils having strongly reduced amounts of particles, as well as of metals, which may impeded their direct use as fuel oils, as well as for further processing.

Claims (19)

1. Claims 1. A porous elongate filter unit for filtering particular matter from a gaseous and/or vapour mixture as obtainable during the pyrolysis of a carbonaceous feedstock, comprising: (i) a first layer of a porous, gas permeable filter medium having an average pore size in the range of from 1pm to 250 pm; (H) a second layer of a porous, gas permeable material having an average pore size in the range of from 1 pm to 250 pm, the layer being positioned in a downstream direction of the gas flow with respect to the first layer; and (Hi) optionally, at least one support layer structurally supporting the first and/or the second layer.
2. 2. A filter unit according to claim 1, wherein layer (i) envelops layer (H).
3. 3. A filter unit according to claim I or claim 2, wherein the porous filter medium comprises a woven or non-woven sheet like material.
4. 4. A filter unit according to any one of the previous claims, wherein the porous filter medium comprises a metal composition that is inert at the reaction conditions.
5. 5. A filter unit according to any one of the previous claims, wherein the porous filter medium comprises one or more mesh structures.
6. 6. A filter unit according to any one of the previous claims, further comprising an axial opening, and an end fitting fixed to the filter medium, the end fitting providing a first end of the filter unit, the end fitting having an end inner surface defining an end fitting opening through the end fitting, the end fitting opening being co-axial with the axial opening of the filter unit; wherein layer (ii) forms a first hollow lumen positioned within the axial opening of the filter unit.
7. 7. A filter unit according to any one of the previous claims, wherein the filter unit has a pyramidal, cylindrical, frustriconical or conical shape.
8. 8. A process for the preparation of filtered gaseous pyrolysis products comprising: (a) providing carbonaceous material to a pyrolysis reactor; (b)heating the carbonaceous material in the pyrolysis reactor under pyrolysis conditions to effect pyrolysis of the material into a gaseous state in a substantially oxygen free and pressure controlled environment; and (c) passing the gases through one or more filter units according to any one of claims 1 to 7, to obtain separated-out particulate matter, and a purified gaseous pyrolysis mixture.
9. 9. A process according to claim 8, further comprising (d) condensing normally liquid products from the purified gaseous mixture, to obtain liquid pyrolysis oil.
10. 10. A process according to claim 8 or 9, wherein the pressure in the pyrolysis chamber is in the range of from 1 to 5 bar.
11. 11. A process according to any one of claims 8 to 10, wherein the heating is conducted at a temperature of between about 350°C and 650°C.
12. 12. A process according to any one of claims 8 toll, further comprising (e) adding of a reactant into the pyrolysis mixture prior to and/or after passing the filter.
13. 13. A process according to any one of claims 9 to 12, further comprising the steps of: (f) subjecting a feed comprising a pyrolysis oil to a hydrodeoxygenation step in the presence of a catalyst comprising an active component on a catalyst carrier that is inert at the reaction conditions, to obtain a product stream comprising a partially deoxygenated pyrolysis oil having s an oxygen content of from 10 to 30 wt%, and (g) separating at least one product fraction from the product stream obtained in (f),
14. 14. A process according to claim 13, further comprising (h) blending the pyrolyis oil obtained in (d) and/or at least one product fraction obtained in (g) with at least another fuel compound and/or an additive to obtain a biofuel.
15. 15. A process according to any one of claims 13 or 14, wherein the hydrodeoxygenation step (f) is carried out in the presence of a hydrocarbon feed derived from a mineral crude oil, to obtain at least one upgraded fuel product fraction comprising biofuel components.
16. 16. A normally liquid biomass pyrolysis oil obtainable by any one of claims 8 to 13, comprising less than 25 ppm of Calcium, less than 10 ppm of potassium, less than 10 ppm of Magnesium, less than 27 ppm of Sodium, less tha 10 ppm of Copper, and/or less than 10 ppm of Aluminium.
17. 17. A pyrolysis apparatus comprising: (a) a pyrolysis reactor chamber that heats and thermally decomposes a carbonaceous feedstock material to generate char and gaseous product comprising normally gaseous, normally liquid and/or aerosol components from the carbonaceous feedstock material, and (b) a filter comprising at least one filter unit according to any one of claims 1 to 7 to essentially remove char and particular matter from a filtered gas and/or vapour stream, and (c) a condenser means for cooling and condensing at least one normally liquid pyrolysis oil fraction from the filtered gas and/or vapour stream, and optionally, (d) a hydropyrolysis, hydrodeoxygenation and/or deoxygenation unit for s treatment of the normally fluid pyrolysis oil traction.
18. 18. An apparatus according to claim 17, further provided with means for providing a reverse pressure pulse to upstream side of the one or more filter units to remove solids and condensed heavy tar from the surface of the first ao porous layer
19. 19. Use of the filter according to any one of claims 1 to 8 for the removal of solid particulate matter from pyrolysis and/or flue gases.