MIXTURE OF STEAM-CRACKED BIOMASS AND LIGNIN FOR GRANULE PRODUCTION

Abstract

A biomass upgrading process comprises a steam-cracking step for producing a granulated combustible product, and, prior to the granulation step, a step of mixing an intermediate pulverulent product resulting from the steam-cracking of the biomass and a pulverulent material having a high lignin content.

Claims

1. A method for biomass exploitation comprising a step of steam-cracking in order to produce a pelleted fuel product, comprising a step of mixing an intermediate pulverulent product originating from the steam-cracking of the biomass, and a pulverulent material having a high lignin content, prior to a pelletizing step, wherein the method comprises a step of steam-cracking to produce an intermediate pulverulent product, and wherein the method further comprises: a step of steam-cracking to produce a steam-cracked biomass, at least 50 wt. % of which is mixed with a ligneous fraction obtained by chemical or biochemical treatment of a residual portion of the steam-cracked biomass, and a pelletizing step for pelletizing the mixture.

2. A method for preparing pellets having a unitary calorific value of greater than more than 10% of an initial biomass, comprising a step of preparing powder by steam-cracking, followed by a pelletizing step, wherein the method comprises a step of mixing steam-cracked pulverulent material and a material comprising at least 50% lignin originating from a second treatment prior to the pelletizing step.

3. The method of claim 2, wherein the material containing at least 50% lignin is a solid co-product having a content greater than an amount of lignin contained in the biomass.

4. The method of claim 3, wherein 2% to 30% of the material containing at least 50% lignin is mixed with an additional quantity of steam-cracked biomass.

5. A system for biomass exploitation including a steam cracker, a pelletizing station, and a transformation station for transforming some steam-cracked products to produce lignin, the method further comprising a feed mechanism for feeding some steam-cracked products and at least some of the lignin produced by the transformation station to the pelletizing station.

6. The method of claim 2, wherein 2% to 30% of the material containing at least 50% lignin is mixed with an additional quantity of steam-cracked biomass.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0036] The present disclosure will be more clearly understood upon reading the following detailed description of a non-limiting embodiment of the disclosure, with reference to the accompanying drawings, in which:

[0037] FIG. 1 is a schematic view of the disclosure.

DETAILED DESCRIPTION

[0038] FIG. 1 is a flow diagram of an installation for implementing the disclosure.

[0039] As shown therein, a method for producing tablets or compacts (also referred to as “black pellets”) from biomass containing lignin, comprises steps including: [0040] (a) pre-treating the biomass (1) in equipment (10) for carrying out a reduction of particles of several cubic centimeters, and optionally carrying out partial drying, in order to achieve the form of dust, sawdust, shavings, fragments, cellulose shavings, flakes, trimmings, or scraps; and [0041] (b) passing the biomass, thus pre-treated, into a reactor (20) in order to heat the particles of biomass to a temperature of from 180° C. to 235° C. by injecting steam (21) into the reactor (20). A first feed chamber (22) carries the biomass toward a reactor (20), which contains an endless screw or allows for passage under the influence of gravity, and carries the hydrolyzed material into the reactor at the temperature reached between 1 to 12 minutes, in order to soften the material and release lignin, as far as an outlet zone (23) provided with a valve (24), allowing for the extraction of the steam-cracked biomass after passing into a lower-pressure zone.

[0042] Optionally, some of the waste gases (25) are recovered for additional exploitation.

[0043] At the output of the reactor (20) a separation is carried out, some of the steam-cracked biomass being introduced into a second reactor (30) ensuring treatment in order to extract compounds having added value, for example, polymeric sugars (cellulose and hemicellulose) or sugars such as glucose or xylose, and furthermore a lignin-rich co-product.

[0044] The lignin-rich co-product is mixed with the steam-cracked biomass in a mixer (40), and then compressed in a pelletizing press (50) in order to form lignin-rich fuel pellets.

[0045] The effect of the steam-cracking treatment is that of destructuring the biomass fiber matrix, which allows for easier release of fermentable monosaccharides.

[0046] It results in the separation of the hemicellulosic fraction, which makes it possible to increase the accessibility of the cellulosic fraction by creating large pores within the fibrous structure, resulting in hydrolysis reactions. It also promotes the reduction in the crystallinity of the cellulose. Various studies show that the thermochemical treatments tend to increase the crystallinity index of the cellulosic fraction, resulting in a reduction in the accessibility of the substrate.

[0047] Finally, the access to the cellulose fibers is greatly restricted by the presence of lignin, which is a matrix that surrounds the cellulosic fraction. Elimination of the lignin is essential in order to carry out hydrolysis operations.

[0048] The installation also provides the possibility of introducing lignin, originating from a remote production site, into the mixer (40) in order to enrich the steam-cracked material with lignin.

[0049] The aim is to produce pelleted fuels having a calorific value at least equal to 5300 kWh/ton, for an initial biomass of 5000 kWh/ton.

[0050] The steam-cracking increases the calorific value by extracting the low-energy volatile oxygenated molecules from the solid residue, which arithmetically increases the calorific value thereof, to reach 5200 to 5400 kWh/ton under acceptable economic conditions. The addition of lignin originating from the co-product of a second reaction and having a calorific value of 7500 kWh/ton, at a level of approximately 2 wt. % to 30 wt. %, makes it possible to increase the qualities of the pellets.

Addition of Lignin Co-Product of Black Liquor

[0051] According to an advantageous variant, the lignin mixed into the steam-cracked biomass is recovered from co-products of the treatment of black liquor produced in the paper-making industry, in order to form a liquid lignin phase.

[0052] Three methods for recovering lignin from black liquor used in the production of paper are conventionally used. The first method, implemented in the 1940s close to a host kraft plant located in Charleston (South Carolina), makes it possible to produce powdered lignin, having the disadvantage of a high salt content. The salt creates problems of a high concentration of cinders in the kilns. Moreover, the high contents of cinders may negatively affect the properties of green chemistry applications containing lignin. Nonetheless, a mixture of 2 to 5% of this lignin with the result of the steam-cracking makes it possible to enrich the calorific value without significant disadvantages.

[0053] The second method, developed since the 1990s, is used in a host pulp mill in Plymouth (North Carolina). This second method produces lignin having a low salt content, which can be used as a fuel. A third method, developed over the past ten years, begins with the production installation in a paper pulp mill in Hinton, Alberta.

[0054] The three technologies use sulfuric acid as a strong acid, which produces significant levels of sodium sulfate in the form of a brine flow. In order to recover the sodium, the sodium sulfate must be incorporated into the paper-making recovery system, by adding sulfur to the charge. A lignin extraction process is necessary in order not to add sulfur to the paper-making.

[0055] Eliminating a fraction (up to 30%) of the lignin from the black liquors allows the pulp and paper mills, which have reached the maximum output in their recovery boilers, to increase their production of the same lignin fraction that is withdrawn and injected into the mixer (40) in order to improve the calorific qualities of the steam-cracked biomass.