Methodology for the removal of inorganic components from biomass of agro/forest/urban origin and from low-quality coal such as peat, lignite, sub-bituminous and bituminous coals

Abstract

A methodology for the removal of the harmful components of the ash of biomass of agro/forest/urban origin and of low-quality coal fuels, as peat, lignite, sub-bituminous and bituminous coals, is invented. The harmful components are alkaline metals, chlorine and sulphur. They are removed before the thermochemical conversion in order to prevent or minimise the corrosion, scaling/deposition, ash agglomeration problems, as well as the alkaline metal, chlorine, sulphur emissions. Furthermore, it aims in the production of materials of low moisture content, low hygroscopicity, which can be easily ground, and mixed with various other materials, easily fed to commercial boilers for energy production, which can be easily pelletised with or without other materials at various proportions and with very low energy requirements. The removal is achieved with pre-pyrolysis/pre-gasification at 250-320 C. for 5 min to 2 h of biomass of agro/forest/urban origin, as well as, of low-quality coal fuels, as peat, lignite, sub-bituminous and bituminous coals. Then the pre-pyrolysed/pre-gasified sample is washed with a 0.5%-20% weight basis aqueous calcium acetate and/or magnesium acetate and/or aluminum acetate and/or ammonium acetate solution. These acetate salts can be mixed in a proportion of 0% to 100% to form an active salt which is used for the preparation of the aqueous solution. Any kind tap water from a public water supply system, spring, etc. can be used for the preparation of aqueous solution. The solid-to-liquid ratio is 33 g/L to 600 g/L, the temperature varies from 13 C. to 95 C., and the treatment duration between 5 min to 24 h.

Claims

1. Method for the removal of inorganic components from raw material, wherein the raw material is selected from the group consisting of biomass of agricultural/forest/industrial origin, low-quality coal fuels selected from the group consisting of lignite, peat, subbituminous, and bituminous coals that are characterized by the presence of large amounts of sulfur (higher than 0.2% in coal dry mass basis), chlorine (higher than 0.01% in coal dry mass basis), alkali metals (higher than 0.1% in coal dry mass basis) and moisture (up to 30-40% in coal wet mass basis) before thermochemical conversion of the material, and any combination thereof, wherein the raw material comprises at least a carboxylic compound containing hydrogen, the method comprises: heating of the raw material at a temperature range between 200 C. and 300 C., for 5 min to 2 h, whereby heating is effected with a small amount of oxygen, air, and combinations thereof up to an amount that is less than 30% of that required for stoichiometrical oxidation/combustion of these materials at temperatures from 200 C. to 300 C. and greater than 0.1%; and washing of the heated raw material with an aqueous solution of at least one of calcium acetate salt, magnesium acetate salt, aluminum acetate salt, ammonium acetate salt, and combinations thereof at concentrations from 0.5% to 20% water weight basis, at a solid to-liquid ratio from 33 g/L up to 600 g/L, at a temperature range between 13 C. and 95 C., the treatment duration being from 5 min to 24h, wherein the washing of the heated raw material results in_hydrogen atoms in the structure of the carboxylic compound replaced with atoms of calcium, magnesium, aluminum, ammonium, and combinations thereof in order to increase the percentage of calcium, magnesium, aluminum, and ammonium into the carboxylic compound and alter its reactivity and ash melting behavior, and wherein, the alkaline metals which are included in the structure of carboxyl components react with calcium/magnesium/aluminum/ammonium acetates and are replaced by calcium/magnesium/aluminum/ammonium in the structure of the organic material.

2. Method according to claim 1, wherein heating is done at temperatures between 250 C. and 300 C.

3. Method according to claim 1, wherein heating is done for a period from 10 min to 40 min.

4. Method according to claim 1, wherein the acetate salts are used in separate aqueous solutions for successive extractions.

5. Method according to claim 1, wherein any kind of water from a public water system is used for the preparation of the aqueous solution.

6. Method according to claim 1, wherein after washing the raw material is dried with a combination of mechanical separation processes and of drying in rotational dryers.

7. Method according to claim 5, wherein the acetate salts are recovered during the drying process and recycled into the process.

8. Method according to claim 1, wherein the raw materials are comprised of sludges from biological waste treatments.

9. Method according to claim 1, where the reactivity of the treated material increases due to the effect caused by the increased concentration of Ca, Mg, NH4, Al ions in the structure of the treated material.

10. Method according to claim 1, where the concentration of calcium/magnesium/aluminum/ammonium increases in the ash of treated material.

11. Method according to claim 1, where the ratio of the inorganic compounds (Ca, Mg, Al, NH4), which can react as catalysts during the process of thermochemical conversion increases.

12. Method according to claim 1, wherein the calcium acetate salt, magnesium acetate salt, aluminum acetate salt, ammonium acetate salt may be used in any combination thereof.

13. Method according to claim 1, where complete elimination of reactive alkali metals and chlorine is realized after the washing of the heated raw material with an aqueous solution of at least one of calcium acetate salt, magnesium acetate salt, aluminum acetate salt, ammonium acetate salt, and combinations.

14. Method according to claim 1, where a reduction of sulfur emissions may be increased to 100%.

Description

EXAMPLE 1

(1) Olive kernel wood from olive kernel oil production plant in Messinia (GR), is pre-pyrolysed at 300 C. for 1 h. Subsequently, washing is applied, with an aqueous calcium acetate solution, 10% (w/w), for 1 h at a solid to liquid ratio 300 g/L, under constant stirring and heating, at 70 C., in a 2 L beaker on a hotplate. Following the pretreatment the sample is filtered and dried at 50 C. Table 1 shows the composition of olive kernel wood before and after the pretreatment, whereas, Table 2 presents the composition of the ash content before and after the pretreatment. Ash analysis showed that the pretreated material does not contain chlorine and alkaline metals at all, the calcium concentration is increased, while the concentration of sulphur is considerably reduced, compared to the initial material.

EXAMPLE 2

(2) Lignite from North Dakota (US), which has high sodium and chloride concentration, is pre-pyrolysed at 300 C. for 1 h. Subsequently, washing is applied, with an aqueous calcium acetate solution, 10% (w/w), for 1 h at a solid to liquid ratio 350 g/L, under constant stirring and heating, at 70 C., in a 2 L beaker on a hotplate. Following the pretreatment the sample is filtered and dried at 50 C. Table 1 shows the composition of olive kernel wood before and after the pretreatment, whereas, Table 2 presents the composition of the ash content before and after the pretreatment. Ash analysis showed that the pretreated lignite does not contain chlorine and alkaline metals at all, the calcium concentration is increased, while the concentration of sulphur is considerably reduced, compared to the initial material.

(3) TABLE-US-00001 TABLE 1 Analysis and characterization of olive kernel wood and lignite Raw olive kernel Raw lignite wood (not Pretreated olive (non Pretreated pretreated) kernel wood pretreated) lignite Proximate Analysis (% d.b.) Moisture 9.5 2.56 21.3 5.15 Ash 4.60 5.58 12.25 10.01 Volatile matter 76.0 29.25 41.77 39.96 Fixed Carbon 19.40 62.68 45.98 50.03 Elemental analysis (% d/b.) Carbon 50.7 72.98 56.34 60.7 Hydrogen 5.89 3.51 4.46 3.58 Nitrogen 1.36 1.79 1.24 1.02 Sulphur 0.3 0.07 1.31 0.73 Chloride 0.18 <0.01 0.2 <0.01 Oxygen 36.97 13.59 24.2 22.89 Heating value 21.21 28.2 23.68 24.34

(4) TABLE-US-00002 TABLE 2 Analysis and characterization of ash from olive kernel wood and lignite Raw olive kernel wood Raw lignite Analysis (not Pretreated olive (non Pretreated (%) pretreated) kernel wood pretreated) lignite SiO.sub.2 32.6 45.38 18.8 29.2 MgO 3.79 5.9 6.14 9.6 Al.sub.2O.sub.3 2.96 4.3 6.9 12.1 CaO 10.22 29.8 18.3 23.4 Fe.sub.2O.sub.3 1.9 1.35 15.16 9.1 TiO.sub.2 0.1 0.15 0.29 0.37 P.sub.2O.sub.5 9.5 8.1 0.3 0.14 K.sub.2O 27.23 0.05 0.72 0.3 Na.sub.2O 4.17 0.01 10.15 0.05 SO.sub.3 4.97 2.48 21.61 15.93 Cl 1.43 <0.01 1.6 <0.01

(5) The described methodology achieves the removal of the harmful components of the ash of biomass of agro/forest/urban origin and of low-quality coal fuels, as peat, lignite, sub-bituminous and bituminous coals. The harmful components are alkaline metals, chlorine and sulphur. They are removed before the thermochemical conversion in order to prevent or minimise the corrosion, scaling/deposition, ash agglomeration problems, as well as the alkaline metal, chlorine, sulphur emissions. Furthermore, it aims in the production of materials of low moisture content, low hygroscopicity, which can be easily ground, and mixed with various other materials, easily fed to commercial boilers for energy production, which can be easily pelletised with or without other materials at various proportions and with very low energy requirements.

(6) In the application of the method, various types of biomass of agro/forest/urban origin and of low-quality coal fuels, as peat, lignite, sub-bituminous and bituminous coals are at pre-pyrolysed/pre-gasified 250-300 C. for 5 min up to 2 h and then, the pre-pyrolysed/pre-gasified sample is washed with a 0.5%-20% weight basis aqueous calcium acetate and/or magnesium acetate and/or aluminum acetate and/or ammonium acetate solution. These acetate salts can be mixed in a proportion of 0% to 100% to form an active salt which is used for the preparation of the aqueous solution. Alternatively, they can be used separately to prepare separate solutions for successive extractions with the same results. The proportions used and the use or not of successive extractions depend on the kind and on the composition of the initial material as well as on the desired properties of the material after treatment. Any kind tap water from a public water supply system, spring, etc. can be used for the preparation of aqueous solution. The solid-to-liquid ratio is 33 g/L to 600 g/L, the temperature varies from 13 C. to 95 C., and the treatment duration between 5 min to 24 h. The solid/liquid ratio, as well as, the temperature and the duration of the process depends on the type of the treated material. Following the washing of the material it is dried in rotating dryers combining mechanical separation and drying. The produced material is free of chlorine and alkaline metals in the form of water soluble salts and salts of organic acids, these constitute the most active type of alkaline metals, which generate emission problems. The treated material also contains significantly lower sulphur (30-80% of the initial content). The calcium/magnesium/aluminium/ammonium acetates are recovered during the drying process of the treated material and recycled in the process.

(7) The above described methodology can be applied in the treatment of any kind of biomass, including of the sludge from sewage plants.