Biofuel product and method for the production thereof

Abstract

The invention relates to a method for producing a biofuel from an aqueous mixture of carbonized biomass obtained by means of a method for the hydrothermal carbonization of biomass, characterized in that it comprises: (a) grinding the aqueous mixture of carbonized biomass until a maximum size of less than 500 micrometers of the particles contained in the mixture is obtained; (b) applying a method for the physical separation of inorganic substances; and (c) reducing the moisture content until a water content of between 25 and 55 wt. % is reached. The invention also relates to the biofuel obtained by said method, and to the use thereof in various applications.

Claims

1. A process for obtaining a biofuel from an aqueous mixture of carbonised biomass obtained in a process for hydrothermal carbonisation of the biomass, comprising the steps of: (a) grinding the aqueous mixture of carbonised biomass, wherein the mixture has a carbon content of at least 60% and a content of volatile substances of between 50 and 70%, expressed on a dry ash-free basis, until a maximum particle size of less than 500 micrometers is obtained; (b) applying a process for physical separation of inorganic substances; and (c) reducing a moisture content until a water content of between 25 and 55 wt. % is reached.

2. The process according to claim 1, further comprising applying a pre-treatment to the aqueous mixture of carbonised biomass, wherein said pre-treatment comprises: (1) a first grinding step of the aqueous mixture of carbonised biomass until a mean particle size of less than 5 mm is obtained; (2) a first separation step of inorganic substances; and (3) a first dehydration step until a water content of less than 50 wt. %. is obtained.

3. The process according to claim 1, further comprising an additional step of mixing and metering in less than 3 wt. % of at least one chemical dispersant.

4. The process according to claim 1, further comprising a step (d) subsequent to step (c) for a further physical separation of inorganic substances, wherein said step (d) consists of a chemical separation process of adding at least one base and/or at least one acid.

5. The process according to claim 1, further comprising adding water or at least one liquid fuel.

Description

BRIEF DESCRIPTION OF THE FIGURES

(1) FIG. 1 represents the diagram of a preferred embodiment of the production process of the BWF.

DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION

(2) A specific and preferred embodiment of the present invention is detailed below in an illustrative and non-limiting manner.

(3) As shown in FIG. 1, the process starts with a pre-treatment of the aqueous mixture of carbonised biomass (2) obtained at the end of the HTC process (1). This pre-treatment comprises a first grinding (3) of the aqueous mixture of carbonised biomass until mean sizes of particles of less than 5 mm are obtained. Following the first grinding (3), a first separation of inorganic substances (4) is carried out for example by means of cleaning in a flotation column, in which separation by the different densities is carried out. Additionally, a step of dehydration (5) is carried out by means of pressing, until a cake (6) is obtained, with a water content of approximately 50 wt. %, said cake being easily storable.

(4) The cake obtained is then subjected to a fine grinding process (7) by colloidal milling until a mean particles size of less than 20 microns is obtained. Subsequently, the mixture obtained is subjected to a step of separating the inorganic substances (8) by flotation. With the aim of dissolving and removing the inorganic elements not separated in the previous step, the mixture is subjected to a subsequent step of chemical cleaning (9) with at least one base (preferably alkaline hydroxides or alkaline earth hydroxides) and/or the addition of at least one acid (for example, a mineral acid such as sulphuric acid, hydrochloric acid, phosphoric acid, etc.) to dissolve and remove inorganic elements.

(5) Following the chemical cleaning, the process comprises a step of dehydration (10) until the water content is reduced to a percentage less than 50 wt. %. The characteristics of the final product are those shown in the following table:

(6) TABLE-US-00003 PCS, (daf) >24 MJ/kg PCS with 30% moisture 17 MJ/kg Carbon (C) (daf, according to >60% (daf) CEN/TS 15104) Hydrogen (H) (daf, according to 5.5-6.5% (daf) CEN/TS 15104) Nitrogen (N) (daf, according to 0.5-2.5% (daf) CEN/TS 15104) Sulphur (S) (daf, according to <0.3% (daf) CEN/TS 15289) Chlorine (Cl) (daf according to <0.3% (daf) CEN/TS 15289) Ash melting point (according to >1250° C. CEN/TS 15289) Ash content, dry base (EN 14775) <8%, preferably <2% Particle size (according to EN149) <500 microns, preferably <20 micrometers Volatile substances (daf, according 50-70% (daf) to EN 15148) Water content (according to EN 25-55% 14774)

Example 1

(7) Different samples of BWF were prepared from coal coming from the HTC process in the Ingelia prototype reactor, as described in ES2339320. The coal was milled and the water content was adjusted to 55 wt. % for its use in the pumping tests.

(8) TABLE-US-00004 Mean Processed C.sup.a H.sup.a N.sup.a S.sup.a particle Sample biomass (wt. %) (wt. %) (wt. %) (wt. %) size (μm) A Orange peel 57 6.1 1.6 0.1 40 B Pruning 60 6.0 2.1 0.1 <10 C Pruning/ 61 6.1 1.9 0.2 b grass .sup.abased on dry coal without ashes; b not determined.

Example 2. Pumping Tests

(9) The samples A-C prepared and characterised in example 1 were subjected to a pumping test. To this end, the mixture was introduced into a tube with a diameter of less than 2.8 cm and extruded through a hole of 2.1 mm. A positive result was reported when 90% or more of the mixture was able to be extruded. It was also visually observed whether a separation of the coal and the water took place after or during the extrusion.

(10) TABLE-US-00005 Sample Extrusion >90% Water separation A Yes.sup.a No B Yes No C Yes No .sup.a65 wt. % water content.
In all cases, the water carbon mixture could be extruded without the addition of dispersant agents due to the hydrophilic surface. The mixtures behave like Bingham fluids and are stables as such. In order to study the pumping behaviour of the mixture with different concentrations, on one occasion an additional 10% (wt. of the final mass) of water was added and in another case an additional 10% (wt. of the final mass) of ethanol was added. The result obtained was an improvement in the fluidity of the mixture, without producing separation of the coal-liquid mixture. In the case of adding liquid organic compounds, such as for example ethanol, the pumping characteristics are improved at ambient temperatures below 0° C., thus reducing the freezing point of the mixture.