FR3097553A1 - PROCESS FOR THE PRODUCTION OF SOLID FUELS FROM END-OF-LIFE WOOD OR WOOD-WASTE - Google Patents

Abstract

The present invention relates to the field of recycling end-of-life wood or waste wood. More particularly, it relates to a process for upgrading biomass consisting of end-of-life wood or waste wood by steam cracking for the manufacture of solid fuels. It makes it possible to recover processed wood intended for material recycling, landfill or incineration.

Description

PROCESS FOR THE PRODUCTION OF SOLID FUELS FROM END-OF-LIFE WOOD OR WASTE WOOD

The present invention relates to the field of recycling end-of-life wood or waste wood. More particularly, it relates to a process for recovering a biomass consisting of end-of-life wood or wood-waste by steam cracking with a view to the manufacture of solid fuels. It makes it possible to recover processed wood intended for material recycling, landfilling or incineration.

Field of invention

The production of energy (electric and thermal) of renewable origin can be done from the environment (sun, wind, tide, swell, geothermal, hydraulic) or from biomass. Apart from biomass, river or dam hydraulics, and geothermal energy, these renewable energies are intermittent unless the means of energy storage are developed. And only biomass constitutes a primary energy that can be transported to its place of transformation into heat and/or electricity. But biomass is actually a sparse, variable and perishable energy.

The transformation of ligno-cellulosic biomass (wood, agricultural residues, co-products of agriculture and agro-industry) into an energy-dense, transportable and easily storable compound makes it possible to develop and consolidate an industrial sector of stationary energy (biofuel used at a fixed point, the home, unlike biofuels) and to reduce environmental impacts (fossil CO ₂ emissions, with biomass without fertilizers or phytosanitary products). The thermal treatment of biomass by steam cracking allows this densification of energy. However, the proliferation of biomass recovery projects generates strong tensions on the wood supply sectors in particular. The current uses for wood fiber (particleboard and stationery), or even for construction wood or solid furniture, are driving prices up. In addition, environmental policies aim to increase the recycling of end-of-life products, and to limit or even ban landfill solutions for waste from the sector. This is why most of the organic by-products from biomass end up in an energy recovery unit, ie in an incinerator.

Professionals in the wood industry use a usage classification distinguishing wood called "A", wood called "B" and wood called "C". It would seem that this classification was developed by ADEME.

The so-called “A” wood is composed of uncoated, untreated wooden packaging waste.

Wood called “B” is made up of non-hazardous wood waste containing a small amount of additives or other materials; glued wood, wood having received a surface treatment (preservation, finish) or coating (wallpaper, melamine, polypropylene, etc.). As such, this category includes panels, furnishing wood, demolition wood free of rubble, etc.

So-called “C” wood is made up of hazardous waste (creosote wood, for example) destroyed in a special waste incineration plant or used in cement kilns.

Today, the type A or B woods most likely to be used as abundant biofuels at low cost consist of natural wood-fiber but also particle boards, plywood, chipboard, as well as additives. organic (resins, glues, sized papers such as melamine, varnish, plastic polymers, etc.). These products, as well as the form of the wood waste used, do not lend themselves to providing the media that promotes granulation after grinding, unless significant quantities of binding and costly additives are added.

In addition, type A wood called "packaging", although mainly made up of planks (pallets, crates) sometimes includes a few chipboard type elements (foot of pallet), or plywood or particle board (OSB, MDF, HDF) . This presence is sufficient to discourage manufacturers of white pellets from manufacturing their product from A wood. destination for the particular consumer who expects a premium, white-beige product. Unless the process is modified (which would make it more expensive) in particular by the use of binder additives, and the wood A is diluted with other natural woods of the resinous type (more binders but more expensive), there is no no ideal solution. Especially since the level of binder additive is limited to 2 or 3% according to the standards of white pellets claimed.

To date, there is no recovery sector for type B wood, which is currently intended for material recycling, landfilling or incineration. As for type A wood, when it is used in combustion, it is only crushed, without being granulated.

Quite surprisingly and contrary to current practices, the inventors propose using woods A and B to make pellets by steam cracking.

The process according to the invention allows the production of solid fuels from ligno-cellulosic biomass consisting of wood A and/or wood B. It consists of a process for recovering ligno-cellulosic biomass consisting at least in part of wood from end of life or non-granulable wood-waste after shredding, characterized in that a step for preparing said biomass is applied, consisting in eliminating at least some of the elements other than wood, then proceeding to a step of processing heat by steam cracking followed by a granulation step.

Advantages of the invention

The present invention therefore proposes a new approach for the recovery of wood that has been transformed, aged or more generally considered to be at the end of its life and intended for material recycling, landfilling or incineration.

Processed woods generally present a modification of the ligno-cellulosic fibers which makes them difficult to exploit. Indeed, waste wood is drier and its intrinsic characteristics are different from those of young wood.

The use of steam cracking as a destructuring solution and leading to chemical and physical modifications promotes the granulation of wood in general, in particular by migrations of binding and sticky lignin in the fibers, a key element of favored granulation. Steam cracking makes it possible to restore the qualities of the lignins.

In addition to the known effect of steam cracking to reduce the fibers to powder and homogenize the biomasses, the effect of the steam treatment makes it possible to destructure the other components present in the wood (glues, resins, additives, etc.) and therefore to participate in a granulometric standardization of the product and a homogeneous distribution of these molecules avoiding singular zones which could be zones of less good efficiency of the granulation. Furthermore, the heat treatment in addition to chemically degrading certain exogenous molecules results in a dark coloring of the product (future black granulate). This coloring attenuates the presence of dyes and pigments added in wood A and B, and contributes to its acceptance by the user.

The process for preparing granules by steam cracking has the advantage of producing granules whose visual appearance is homogeneous and constant, which is a mark of quality for the consumer.

The method more generally allows better granulation than in the case of the preparation of white granules from the same substrate.

The process avoids the use of additives or the use of expensive additional natural resinous wood to promote the cohesion of the pellets.

Finally, the process using wood A and wood B favors local sectors which recover and recycle this aged wood rather than incinerating it.

Detailed description of the invention

An object of the invention relates to a process for the recovery of lignocellulosic biomass consisting at least in part of end-of-life wood or non-granulable wood-waste after grinding, characterized in that a step of preparing said biomass consisting of eliminating at least some of the elements other than wood, then proceeding to a heat treatment step by steam cracking followed by a granulation step.

By "end-of-life wood or wood-waste", we mean any processed or aged wood, more particularly wood qualified as wood A or wood B according to the ADEME classification. This wood is not granulable directly after grinding.

The objective of the wood preparation stage is to reduce the final contaminant content.

By “contaminant”, we mean any substance detected in a place where it is not normally found. In the case of contaminated wood, it is any substance that is not found naturally in the wood. Examples of contaminants frequently found in wood are paint, plastic (coating, decoration, handle, buttons, etc.), metals (nails, hinges, locks, etc.), glass, glue-type additives, resins, polymers, phytosanitary products, melamine, etc.

The preparation of the wood consists in removing the residues of glass or metals or plastics or mineral residues. It can be implemented by optical, densimetric, magnetic or mechanical sorting. This processing can be done manually or automatically.

In general, these treatments must be simple to implement and inexpensive for the process for producing black granules to be economically viable.

It is possible in particular that the treatment consists of removing certain wood that is too contaminated. Indeed, it is recommended to carry out a selection of wood A and B, and especially a fine selection of wood B to avoid the presence of too many non-binding exogenous elements for granulation, in particular plastics. Obviously, the presence of inerts (locksmith metals, glass, etc.) as well as polymers (plastic plating, PVC fields, etc.) is to be avoided. Also the supply chain will have to include sorting and selection operations. Afterwards, the process must include a good phase of securing the tools (grinding, iron removal, stone removal to remove heavy material pollutants, possibly sorting and visual verification), then the process becomes classic again with possibly drying, then steam cracking and granulation.

Although this possibility is not preferred, it is possible, for the most contaminated wood, to add certain additives and/or to mix with noble natural wood such as softwood; these solutions have a cost and lead to different constraints, which must be assessed and quantified in terms of benefit/risk before implementing them.

The producers of black pellets obtained from wood A or wood B are industrialists who seek to optimize the production of biofuels by using local resources from the recovery and recovery of end-of-life wood, thus benefiting from a tariff of lower purchase, but still the easy use of the product in biomass boilers, and economically replacing coal or gas, to date inexpensive fuels, and participating in a circular and environmentally friendly ecology.

Users of black pellets obtained from wood A or wood B are all users of biomass boilers.

Claims (3)

Process for the recovery of ligno-cellulosic biomass consisting at least in part of end-of-life wood or non-granulable wood-waste after grinding, characterized in that a step of preparing said biomass is applied consisting in eliminating at least one part of the elements other than wood, then to proceed to a step of heat treatment by steam cracking followed by a step of granulation. Process according to Claim 1, in which the said preparation step consists in removing the glass or metal or plastic residues or mineral residues by optical, densimetric, magnetic or mechanical sorting. Process according to one of Claims 1 or 2, in which the said biomass consists exclusively of end-of-life wood or non-granulable wood-waste after shredding.