Method of production of fuels from biomass, from low quality coals and from wastes, residues and sludges from sewage treatment plants

Abstract

The present invention concerns a method for the removal of inorganic components such as potassium, sodium, chlorine, sulfur, phosphorus and heavy metals, from biomass of rural or forest or urban origin or even mixture of different origin biomasses, from low quality coals such as peat, lignite and sub-bituminous/bituminous coals, from urban/industrial origin residues/wastes, which are possible to include as much organic>5% weightas inorganic<95% weightcharge and from sewage treatment plant sludges. The desired goal is achieved with the physicochemical treatment of the raw material. The method can also include the thermal treatment, which can precede or follow the physicochemical one. The application of the thermal treatment depends on the nature and the particular characteristics of each raw material as well as on the feasibility analysis of the whole process in order to determine the optimization point in each case.

Claims

1. A method for the removal of inorganic components from raw material for the production of clean materials, wherein the raw material is selected from the group consisting of biomass, coals, and residues from agricultural, urban, or industrial origin, wastes from urban or industrial origins, sludges from sewage treatment plants, and any combination thereof, the method comprising: thermally treating the raw material in a nitrogen atmosphere in the presence and/or absence of air at temperatures of from about 200 C. to about 320 C. for a residence time at the temperature from about 5 minutes to about 2 hours; and washing the raw material with an aqueous solution that contains salt at temperatures ranging from about 13 C. to about 95 , wherein the aqueous solution is comprised of organic and/or inorganic salts containing at least one of calcium, magnesium, aluminum, titanium, ammonium cations, and combinations thereof.

2. The method as set forth in claim 1, wherein the thermal treatment is performed at the temperature range for a residence time of about 5 minutes to about 40 minutes, and wherein the moisture content of raw material is smaller than 30% in wet basis.

3. The method as set forth in claim 1, wherein the thermal treatment is performed in a nitrogen atmosphere and the presence of oxygen and/or air, which is limited in less than 40% of the amount that is required for the stoichiometric combustion of these materials.

4. The method as set forth in claim 1, wherein the raw material comprises at least a carboxylic compound containing hydrogen and selected from the group consisting of organic acids, organic salts, and combinations thereof, wherein the carboxylic compound constitutes part of the structure of the raw material, the method further comprising replacing the hydrogen atoms in the structure of the carboxylic compound with atoms of inorganic elements by means of a chemical reaction between the atoms of the inorganic element and the hydrogen atoms.

5. The method as set forth in claim 1, wherein the concentration of salt in the aqueous solution is in the range of from about 0.1% to about 30% w/w in water volume.

6. The method as set forth in claim 1, wherein the concentration of salt in the aqueous solution is in the range of rom about 0.1% to about 2% w/w/in water volume.

7. The method as set forth in claim 1, wherein the aqueous solution is further comprised of at least one of an organic acid, an inorganic acid, and combinations thereof.

8. The method as set forth in claim 7, wherein the concentration of salt and acid in the aqueous solution is in the range of from about 0.1% to about 30% w/w in water volume.

9. The method as set forth in claim 7, wherein the concentration of salt and acid in the aqueous solution is in the range of from about 0.1% to about 2% w/w in water volume.

10. The method as set forth in claim 1, wherein the aqueous solution is comprised of at least one of calcium acetate salts, magnesium acetate salts, aluminum acetate salts, ammonium acetate salts, titanic acetate salts, and combinations thereof.

11. The method as set forth in claim 7, wherein the aqueous solution is comprised of at least one of citric acid, malic acid, benzoic acid, phosphoric acid, nitric acid, and combinations thereof.

12. The method as set forth in claim 1, wherein the washing is performed at a ratio of raw material to aqueous solution in the range of from about 33 g/l to about 600 g/l.

13. The method as set forth in claim 1, wherein the washing is performed at a ratio of raw material to aqueous solution in the range of from about 150 g/l to about 400 g/l.

14. The method as set forth in claim 1, wherein the washing is performed at temperatures of about 55 C. to about 80 C.

15. The method as set forth in claim 11, wherein the washing is performed for a period of about 5 minutes to about 24 hours.

16. The method as set forth in claim 1, wherein the washing is performed for a period of about 10 minutes to about 35 minutes.

17. The method as set forth in claim 1, wherein the washing is performed in different aqueous solutions in succession.

18. The method as set forth in claim 1 wherein the thermal treatment is performed at least one of prior to washing of the raw material and after washing of the raw material.

Description

EXAMPLE 1

(1) Olive kernel wood from an olive kernel oil production plant in Messinia (GR) is prepyrolysed at 300 C. for 1 h in a lab-scale fixed-bed reactor in nitrogen atmosphere. Subsequently, washing with an aqueous calcium acetate solution 10% (w/w) is applied for 1 h at a solid to liquid ratio 300 g/l using tap water, under constant stirring in a 2 L beaker and constant heating at 70 C. on a hotplate. After the pretreatment, the sample is filtered and dried at 50 C. Table 1 (see column denoted olive kernel wood-1) shows the composition of olive kernel wood before and after the pretreatment while Table 2 presents the composition of its ash content before and after the pretreatment. The analysis of the pretreated material shows an increase in the fixed carbon and heating value while the volatile matter and oxygen content is decreased. Ash analysis of the olive kernel wood showed that the pretreated material does not contain chlorine and alkali metals almost at all in water soluble and/or ion-exchange form, calcium concentration is increased, while sulfur concentration is considerably reduced compared to the initial material.

(2) In addition to the previous pretreatment the olive kernel wood is prepyrolysed at 300 C. for 35 min in a lab-scale fixed-bed reactor in nitrogen atmosphere. Subsequently, washing with an aqueous calcium citrate solution 0.4% (w/w) is applied for 20 min at a solid to liquid ratio 150 g/l using deionized water, under constant stirring in a 2 L beaker and constant heating at 30 C. on a hotplate. After the pretreatment, the sample is filtered and dried at 50 C. Table 1 (see column denoted olive kernel wood-2) shows the composition of olive kernel wood before and after the pretreatment while Table 2 presents the composition of its ash content before and after the pretreatment. The properties of the specific material is seen to be similar to those of previous olive kernel wood-1 material although the thermal treatment period now is half compared to the case of the olive kernel wood-1 material. Ash analysis of the olive kernel wood-2 material showed that the pretreated material does not contain chlorine and alkali metals almost at all in water soluble and/or ion-exchange form, calcium concentration is increased, while sulfur concentration is considerably reduced compared to the initial material.

EXAMPLE 2

(3) Lignite from North Dakota (US), which has high sodium and chlorine concentration, is pre-pyrolysed at 300 C. for 1 h in a lab-scale fixed-bed reactor in nitrogen atmosphere. Subsequently, washing with an aqueous calcium acetate solution 10% (w/w) is applied for 1 h at a solid to liquid ratio 350 g/l using tap water, under constant stirring in a 2 L beaker and constant heating at 70 C. on a hotplate. After the pretreatment, the sample is filtered and dried at 50 C. Table 1 shows the composition of the lignite sample before and after the pretreatment while table 2 presents the composition of its ash content before and after the pretreatment. Ash analysis of the lignite sample showed that the treated material does not contain chlorine and alkali metals at all, calcium concentration is increased, while sulfur concentration is considerably reduced, compared to the initial material.

(4) TABLE-US-00001 TABLE 1 Analysis and characterization of olive kernel wood and lignite Raw olive Pretreated Pretreated kernel olive kernel olive kernel Raw Pretreated wood wood-1 wood-2 lignite lignite Proximate analysis (% d.b.) Moisture 9.5 2.56 2.45 21.3 5.15 Ash 4.60 5.58 5.3 12.25 10.01 Volatile 76.0 29.25 30.3 41.77 39.96 matter Fixed 19.40 65.17 64.4 45.98 50.03 carbon Elemental analysis (% d.b.) Carbon 50.7 72.98 71.5 56.34 60.7 Hydrogen 5.89 3.51 3.71 4.46 3.58 Nitrogen 1.36 1.79 1.58 1.24 1.02 Sulfur 0.3 0.07 0.05 1.31 0.73 Chlorine 0.18 <0.01 <0.01 0.2 <0.01 Oxygen 36.97 16.07 17.86 24.2 22.89 Heating 21.21 28.2 28.00 23.68 24.34 value Pretreated olive kernel wood-1: prepyrolysed in 300 C. for 1 h Pretreated olive kernel wood-2: prepyrolysed in 280 C. for 30 min

(5) TABLE-US-00002 TABLE 2 Ash analysis and characterization of olive kernel wood and lignite Raw olive Pretreated Pretreated Analysis kernel olive kernel olive kernel Raw Pretreated (%) wood wood-1 wood-2 lignite lignite SiO.sub.2 32.6 22.18 20.38 18.8 29.2 MgO 3.79 5.9 3.9 6.14 9.6 Al.sub.2O.sub.3 2.96 4.3 6.15 6.9 12.1 CaO 10.22 43.8 33.4 18.3 23.4 Fe.sub.2O.sub.3 1.9 1.35 1.3 15.16 9.1 TiO.sub.2 0.1 0.15 0.12 0.29 0.37 P.sub.2O.sub.5 9.5 8.1 4.95 0.3 0.14 K.sub.2O 27.23 0.05 0.07 0.72 0.3 Na.sub.2O 4.17 0.01 0.015 10.15 0.05 SO.sub.3 4.97 2.48 2.41 21.61 15.93 Pretreated olive kernel wood-1: prepyrolysed in 300 C. for 1 h Pretreated olive kernel wood-2: prepyrolysed in 280 C. for 30 min

EXAMPLE 3

(6) A fraction, which contains mainly plastics/polymers as well as some paper, leather and inorganic materials, from partially treated solid urban wastes of Athens is considered. This fraction is prepyrolysed at 300 C. for 1 h and then washed with an aqueous calcium acetate solution 2% (w/w) for 1.5 h at 70 C. at a solid-to liquid ratio 250 g/l using tap water under constant stirring in a 2 L beaker and constant heating at 70 C. on a hotplate. After the pretreatment, the sample is filtered and dried at 50 C. Table 3 shows the composition of the urban waste fraction before and after the pretreatments while Table 4 presents the composition of its ash content before and after pretreatment. Ash analysis of the sample showed that the pretreated material does not contain chlorine and alkali metals at all, while the concentrations of sulfur as well as of heavy metals are considerably reduced compared to the initial material.

(7) TABLE-US-00003 TABLE 3 Analysis and characterization of urban wastes fraction Pretreated Fraction of fraction of urban wastes urban wastes Proximate analysis (% d.b.) Moisture 16.7 2.9 Fixed carbon 7.9 53.9 Volatile matter 80.8 32.9 Ash 11.3 13.2 Elemental analysis (% d.b.) Carbon 47.6 69.09 Hydrogen 6.6 3.5 Nitrogen 0.2 0.15 Sulfur 0.3 0.16 Oxygen 38 13.9 Heating value 20.18 27.24

(8) TABLE-US-00004 TABLE 4 Ash analysis and characterization of urban wastes fraction Pretreated Fraction of fraction of Analysis (%) urban wastes urban wastes SiO.sub.2 37.8 45.69 MgO 2.9 3.2 Al.sub.2O.sub.3 24.7 18.6 CaO 16.9 24.5 Fe.sub.2O.sub.3 1.3 0.97 TiO.sub.2 4.6 3.4 P.sub.2O.sub.5 0.8 0.4 K.sub.2O 1.7 <0.1 Na.sub.2O 4.5 <0.1 SO.sub.3 5.8 3.24 Cl 3.8 <0.01 ZnO 330 ppm 185 ppm PbO 52.4 ppm 37.4 ppm Cr.sub.2O.sub.3 140 ppm 105.8 ppm CuO 80 ppm 63.5 ppm

EXAMPLE 4

(9) A number of rural wastes and residues which includes the olive kernel wood, the wheat straw, the by-product of bioethanol production from corn (DDGS) and the switchgrass suffer washing with an aqueous calcium acetate solution 3% (w/w) for 1 h at a solid-to liquid ratio 200 g/L using distilled water under constant stirring in a 2 L beaker and constant heating at 60-70 C. on a hotplate. After the pretreatment, the sample is filtered and dried at 50 C. Subsequently, the initial raw samples as well as the pretreated ones are ashed in a high temperature oven at 600 C. Afterwards the produced ashes are heated up in the same high temperature oven so that their fusion point is determined. The heating process includes the ash heating at 800 C. initially for one hour and then the progressive heating at higher temperatures using a temperature step of 100 C. up to the determination of the fusion point, which is declared with the change in the natural shape of each sample and its vitrification. Table 5 presents the ash fusion points for the raw as well as for the pretreated biomass feedstock. As it can be seen in table 5, the ash fusion point of the pretreated materials is increased above 500 C. on average due to the removal of alkali metals, chlorine, sulfur and phosphorus during the pretreatment. The best thermal behavior is observed in case of wheat straw, which is considered the most difficult biomass feedstock for thermochemical conversion Worldwide.

(10) TABLE-US-00005 TABLE 5 Thermal behavior of the ash from raw and pretreated biomass feedstock Ash samples Fusion Point ( C.) Raw olive kernel wood 850 Prertreated olive kernel wood 1400 Raw wheat straw 800 Pretreated wheat straw 1500 Raw DDGS 800 Pretreated DDGS 1350 Raw switchgrass 850 Pretreated switchgrass 1400

EXAMPLE 5

(11) A number of rural wastes and residues which includes the olive kernel wood, the wheat straw, the by-product of bioethanol production from corn (DDGS) and the switchgrass suffer washing with an aqueous solution 0.5% (w/w) of citric acid (80%) and magnesium citrate (20%) for 10 min at a solid-to liquid ratio 150 g/L using distilled water under constant stirring in a 2 L beaker and constant heating at 20 C. on a hotplate. Furthermore, the olive kernel wood and the switchgrass suffer washing with an aqueous of aluminum acetate solution 0.5% (w/w) for 10 min at a solid-to liquid ratio 300 g/L in the case of the olive kernel wood and 150 g/L in the case of the switchgrass using distilled water under constant stirring in a 2 L beaker and constant heating at 20 C. on a hotplate. After the pretreatment, the sample is filtered and dried at 50 C. Subsequently, the initial raw samples as well as the pretreated ones are ashed in a high temperature oven at 600 C. Afterwards the produced ashes are heated up in the same high temperature oven so that their fusion point is determined. The heating process includes the ash heating at 800 C. initially for one hour and then the progressive heating at higher temperatures using a temperature step of 100 C. up to the determination of the fusion point, which is declared with the change in the natural shape of each sample and its vitrification. Table 6 presents the ash fusion points for the raw as well as for the pretreated biomass feedstock. As it can be seen in Table 6, the ash fusion point of the pretreated materials is increased above 500 C. on average due to the removal of alkali metals, chloride, sulfur and phosphorus during the pretreatment. When the aluminum acetate salt is used as the solvent for the extraction of the inorganic elements it is seen that the ash melting point of the olive kernel wood and the switchgrass increases an additional 150 C. compared with the case when the citric acid and magnesium citrate salt is use as well as the calcium acetate is used as it is described in Table 5 in example 4. In that case the ash melting temperature of the olive kernel wood and the switchgrass is seen to be even better compared to wheat straw as it is seen in Table 6.

(12) TABLE-US-00006 TABLE 6 Thermal behavior of the ash from raw and pretreated biomass feedstock: Ash samples Fusion Point ( C.) Raw olive kernel wood 850 Pretreated olive kernel wood (A) 1400 Pretreated olive kernel wood (B) 1550 Raw wheat straw 800 Pretreated wheat straw (A) 1500 Raw DDGS 800 Pretreated DDGS (A) 1350 Raw switchgrass 850 Pretreated switchgrass (A) 1400 Pretreated switchgrass (B) 1550 (A) With citric acid and magnesium citrate (80/20%) (B) With aluminum acetate

(13) The invention concerns a method for the removal of the harmful components which are included in raw materials, i.e. in biomass of agro/forest/urban origin, in low quality coals such as peat, lignite and sub-bituminous/bituminous coals, in urban/industrial origin residues/wastes and in sludges from sewage treatment plants. The removal is effected before the thermochemical incineration, combustion, gasification, pyrolysis of these materials.

(14) The method may replace the hydrogen atoms in the structure of the carboxylic compound, which are found in the raw material with atoms of inorganic elements. The method removes the inorganic elements from the carboxylic compounds being present the raw material and replaces them with other elements.

(15) During the physicochemical pretreatment of the raw materials, the materials are washed with an aqueous solution of organic and/or inorganic substances. Any water soluble calcium, magnesium, aluminum, titanium and ammonium salts may be used for the preparation of the aqueous solution for washing of the material. The salts may be combined with any water soluble organic acids, monocarbonic and/or polycarbonic, saturated and/or unsaturated, those having an aromatic ring as well as inorganic acids such as phosphoric acid and nitric acid. The proportions of the salts and acids are 0.1% to 30% weight in the aqueous solution.

(16) The organic and/or inorganic acids and their water soluble salts can be mixed in proportions that vary from 0% up to 100% in order to form the active solvent that will be used in the preparation of the aqueous solution. In addition, they can be used for successive extractions so that the desired result is achieved.

(17) The physicochemical stage is used for the production of clean materials with substantially lower problems during their hermochemical incineration, combustion, gasification and pyrolysis. In particular the application of a method according to the invention results in materials that show very low to zero corrosion, deposition and ash agglomeration problems, very low to zero gas emissions (potassium, sodium, chlorine, sulfur and phosphorus) and heavy metals (Cu, Pb, Zn, Cr, Hg), during the thermochemical incineration, combustion, gasification, pyrolysis of the raw materials.