JP2018111090A - Cleaning method of biomass and method of manufacturing solid fuel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a simple and inexpensive biomass cleaning method without requiring even special equipment, and a method of manufacturing a solid fuel of using the cleaning method of biomass.SOLUTION: A biomass cleaning method includes an immersion process (step S1) of removing alkaline metal included in biomass by immersing the raw biomass in an acid solution. The acid solution is 4.0 or less in pH when finishing the immersion process, and is 2.5 or less, and desirably 2.0 or less in the pH when starting the immersion process, and is more desirably 1.8 or less, and is desirably a sulfuric acid solution in the acid solution. Semi-carbide or carbide of a biomass cleaning object can be provided by a semi-carbonization/carbonization process (step S4).SELECTED DRAWING: Figure 4

Description

  The present invention relates to a method for cleaning biomass and a method for producing solid fuel.

  As a method for effectively using biomass, a method is known in which biomass is carbonized or semi-carbonized and used as an alternative fuel for coal. In this method, the presence of potassium or sodium that adversely affects combustion is a problem. Therefore, when biomass containing a large amount of potassium or sodium is used as a raw material, potassium or sodium is removed prior to carbonization or semi-carbonization of the biomass or after carbonization or semi-carbonization (see, for example, Patent Document 1 and Patent Document 2). .

  Patent Document 1 discloses a method for drying and washing crushed biomass after pressure treatment as a suitable method for removing alkali metals such as potassium and sodium from biomass. In an empty palm bunch (EFB) Examples in which potassium is reduced to 0.24 mass% are described.

  On the other hand, Patent Document 2 states that it is not effective to depotassulate biomass at the raw material stage, and alkali metal can be removed by high-heat treatment of biomass and cell destruction.

JP 2010-270320 A Japanese Patent No. 4894650

  In Patent Document 1, as an example, in an empty fruit bunch (EFB) of oil palm, potassium is reduced to 0.24 mass% when dried and washed after pressure treatment, and is dried at 110 ° C. and then washed to wash potassium. It is described that it decreases to 0.98 mass%. According to the Example of patent document 1, even when the removal rate is highest in the empty fruit bunch (EFB) of oil palm, 0.24 mass% of potassium is contained. Although there is a request to further reduce the concentration of alkali metals such as potassium and sodium depending on the application and use destination, the method described in Patent Document 1 is not sufficient.

  In order to perform pressure treatment or drying treatment, pressure equipment and drying equipment are required, but large-scale equipment is required to process a large amount of biomass such as oil palm empty fruit bunch (EFB). Thus, the processing cost is increased.

  In Patent Document 2, it is possible to remove alkali metals by high heat treatment of biomass and cell destruction, but when we conducted experiments, alkali metals, particularly potassium, could not be removed sufficiently.

  An object of the present invention is to provide a simple and inexpensive method for cleaning biomass that does not require special equipment, and a method for producing a solid fuel using the method for cleaning biomass.

  The present invention is a biomass washing method characterized by including a dipping step of immersing raw biomass in an acidic solution and removing alkali metals contained in the biomass.

  In the biomass cleaning method of the present invention, the acidic solution has a pH of 4.0 or less at the end of the dipping step, and a pH of 2.5 or less, preferably 2.0 or less at the start of the dipping step. More preferably, it is 1.8 or less.

  In the biomass cleaning method of the present invention, the acidic solution is a sulfuric acid solution.

  In addition, the present invention is a method for producing a solid fuel, comprising a semi-carbonization / carbonization step of semi-carbonizing or carbonizing a biomass washed product obtained by the biomass cleaning method.

  According to the present invention, it is possible to provide a simple and inexpensive method for cleaning biomass without requiring special equipment, and a method for producing solid fuel using the method for cleaning biomass.

It is a figure which shows the procedure of the washing | cleaning method of the biomass of this invention. It is a schematic diagram of the washing | cleaning apparatus 1 for enforcing the washing | cleaning method of biomass of this invention. It is a schematic diagram of the washing | cleaning apparatus 2 for enforcing the washing | cleaning method of biomass of this invention. It is a figure which shows the procedure of the manufacturing method of the solid fuel of this invention. It is a photograph of the sample before and behind the sulfuric acid solution immersion test of Examples 1-3 of the present invention.

  The biomass cleaning method of the present invention has the greatest feature in that the biomass is immersed in an acidic solution to remove alkali metals contained in the biomass. Hereinafter, the biomass cleaning method will be described in accordance with the procedure of the biomass cleaning method of the present invention shown in FIG.

  The biomass that is the cleaning object of the present invention is not limited to a specific biomass and can be applied to a wide range of biomass. Specifically, woody biomass such as waste wood, thinned wood, garden trees, bamboo, bark, sawdust, construction waste, straw, sugarcane, sugarcane, corn, banana, rice bran, grass, chaff, rice straw, palm palm Agricultural and plant biomass such as cereals, berries, seeds and coconut shells.

  Since the method for cleaning biomass according to the present invention is excellent in potassium and sodium removal performance, it can be suitably used for biomass containing potassium and sodium at high concentrations. Examples of biomass containing potassium and sodium at high concentrations include palm fruit empty fruit bunches (EFB), which are by-products of palm oil, and grericidia, which is a leguminous tree of Sri Lanka. In addition, regarding palm palm, fiber objects around the fruit, palm palm shell (PKS), trunk, pruned branch, and the like are objects to be cleaned of the present invention.

  The biomass that is the object to be cleaned is used as it is. Raw as used herein refers to biomass that has not been subjected to pretreatment such as water washing, drying (excluding natural drying), heating, pressurization, semi-carbonization, carbonization for the purpose of removing potassium and sodium. Say. Although it does not exclude the method of washing the biomass with water for the purpose of removing potassium and sodium and immersing the washed biomass in an acidic solution, the number of steps increases. The biomass cleaning method of the present invention can sufficiently remove potassium and sodium by a one-step cleaning operation in which raw biomass is immersed in an acidic solution.

  It is not preferable to use a carbide or semi-carbide of biomass as the cleaning object of the present invention. As shown in the Examples section below, in the washing test for Gliricidia, when the Gliricidia was semi-carbonized without washing, the chlorine could be removed to the level of washing the raw wood, but sodium, potassium On the contrary, it was concentrated without being removed. Moreover, compared with the method of washing raw wood with water, the method of washing with water after semi-carbonization had a lower removal rate of sodium and potassium. This is presumed to be due to water repellent by semi-carbonizing and water not reaching the details.

  There is no particular limitation on the form of biomass that is the object to be cleaned. Therefore, the biomass may be used as it is. The original form refers to the form of the collected state and the state of the recovered state, including those obtained by dividing, separating, and cutting the biomass that has been collected and recovered from the viewpoint of transportation, handling, etc. Excluded are those crushed and crushed for the purpose of miniaturization. Even if raw biomass is used in its original form as shown in the examples described later, the alkali metal can be sufficiently removed.

  From the viewpoint of increasing the specific surface area, it is preferable to crush or pulverize the biomass. A biomass original product, a crushed product, or a pulverized product may be used as an object to be cleaned, and a mixture of two or more of the original product, crushed product, and pulverized product may be used as an object to be cleaned.

  As a first step, a biomass original product or the like is immersed in an acidic solution (step S1). This removes potassium, sodium, and the like. When biomass is immersed in an acidic solution, potassium that is difficult to remove can be sufficiently removed. On the other hand, the method of immersing biomass in water cannot sufficiently remove alkali metals, particularly potassium. This difference seems to be due to the fact that the metal ions are easily eluted by lowering the pH by adding acid.

  The acidic solution has a higher alkali metal removal rate when the pH is lower, as shown in the examples described later. The acidic solution has a pH at the end of immersion of 4.0 or less and a pH at the start of immersion of 2.5 or less, preferably 2.0 or less, more preferably 1.8 or less. If it is the conditions of the said pH, it is not necessary to control so that pH may become a constant value during an immersion process.

  In the acidic solution, sulfuric acid (sulfuric acid solution) can be suitably used as the acid component. In view of the fact that metal ions can be easily eluted by lowering the pH, it is possible to use other acidic solutions such as hydrochloric acid in addition to the sulfuric acid solution. However, after removing costs, potassium, sodium, etc. The sulfuric acid solution is preferable from the viewpoint of the use of biomass and the post-treatment of the solution.

  Although the immersion time is not particularly limited, potassium removal rate of 98.7% or more could be obtained by immersion for 1 day as shown in Examples described later. The immersion temperature is not particularly limited, and may be atmospheric temperature. Moreover, although stirring operation is not denied, it is not necessary to perform stirring.

  After the biomass is immersed in the acidic solution, it is recovered and washed with water, the acidic solution adhering to the biomass is washed away, and the acidic solution that has entered the cell membrane of the biomass is preferably replaced with water (step S2). The water used for washing is not particularly limited. The washing procedures such as washing time and presence / absence of stirring are not particularly limited.

  After washing with water, drying may be performed as necessary (step S3). Of course, depending on the form of use thereafter, the drying operation is unnecessary.

  It is known that EFB of common palm palm contains 1 to 3% (dry base) of potassium. The palm palm EFB contains sodium and chlorine in addition to these, but these have a lower content than potassium and are easier to remove than potassium. Even such biomass with a high potassium content can be sufficiently removed by using the cleaning method of the present invention.

  On the other hand, in the method of washing with water after semi-carbonizing the biomass, the method of washing with water after pulverizing the semi-carbide, or the method of washing with water and then washing with warm water after pulverizing the semi-carbide, as shown in the column of Examples below However, sodium and potassium could not be removed sufficiently.

  As described above, the method for cleaning biomass according to the present invention can be easily carried out because the operation is simple and no special equipment is required. FIG. 2 is a schematic diagram of a cleaning apparatus 1 for implementing the biomass cleaning method of the present invention, and FIG. 3 is a schematic diagram of a cleaning apparatus 2 for implementing the biomass cleaning method of the present invention.

  The cleaning apparatus 1 includes an acid-resistant mesh-like container 11 that contains biomass 5, an acid tank 13 that can store the mesh-like container 11 and stores an acidic solution 6, and a water tank that stores cleaning water 7. 15 and a circulation pump 17 for stirring the water in the water tank 15. Movement is facilitated by attaching a rope 21 with a hook to the mesh container 11.

  In order to wash the biomass using the washing apparatus 1, the biomass 5 is put into a mesh-like container 11 (FIG. 2 (a)), and this is immersed in an acidic tank 13 storing the acidic solution 6 for a predetermined time (FIG. 2). (B)) After that, the container 11 is moved to the water tank 15 (FIG. 2 (c)), and the acidic solution 6 adhering to the biomass and the acidic solution 6 that has entered the cell membrane are replaced with water 7. Since the water tank 15 includes a circulation pump 17 that stirs the water 7, the acid solution 6 that has entered the cell membrane of the biomass 5 can be efficiently replaced with the water 7 by operating this pump.

  The cleaning device 2 differs from the cleaning device 1 in the shape of a tank or the like, but the basic configuration is the same. The cleaning device 2 includes an acid-resistant net bag 12 that contains the biomass 5, an acid tank 14 that can store the net bag 12 and stores the acidic solution 6, a water tank 16 that stores the cleaning water 7, and water And a circulation pump 18 for stirring the water in the tank 16. The method of use is the same as that of the cleaning apparatus 1.

  If this cleaning method is further simplified, it is only necessary to provide a pool, put a sulfuric acid solution into it, and immerse the biomass in it, which is suitable for cleaning biomass with a large amount of discharge, such as palm palm EFB. is there.

  Next, the manufacturing method of the solid fuel of this invention is demonstrated based on FIG. Here, the biomass from which the alkali metal has been removed by the biomass cleaning method shown in FIG. 1 is used, and this is semi-carbonized or carbonized to obtain a solid fuel (step S4).

  Semi-carbonization is thermally decomposed at a temperature of about 200 to 350 ° C. in an oxygen-free atmosphere or a low-oxygen atmosphere, and is also referred to as refracting, burning, or low-temperature carbonization. In contrast, carbonization is thermally decomposed at a temperature of about 350 to 600 ° C. in an oxygen-free atmosphere or a low-oxygen atmosphere.

  Biomass semi-carbides or carbides from which alkali metals have been removed by the cleaning method of the present invention can be suitably used as fuel because potassium, sodium, chlorine, etc. are sufficiently removed. In addition, since the solid fuel production method of the present invention is easy to operate and does not require special equipment, the solid fuel can be produced at low cost.

  The biomass washing method according to the present invention and the solid fuel production method according to the present invention are not limited to the above-described embodiment, and can be used without departing from the spirit of the present invention.

  As described above, the preferred embodiments have been described with reference to the drawings. However, those skilled in the art will readily understand various changes and modifications within the obvious scope by looking at the present specification. Therefore, such changes and modifications are interpreted as being within the scope of the invention defined by the claims.

Object to be cleaned As raw biomass, an EFB original product of palm palm (an EFB original fixed product) and an EFB crushed product obtained by crushing an EFB original product of palm palm were used as raw biomass. The original EFB product was obtained by vertically cutting the recovered palm palm EFB and cutting it to about 10 g per piece (see the photograph in FIG. 5). The size of the EFB crushed product is about 1 to several tens of mm.

  The potassium content of the EFB original product of palm palm was 9000 to 11000 mg / kg-dry base, and the potassium content of the EFB crushed product of palm palm was 11000 mg / kg-dry base. For analysis of potassium, wet decomposition-flame atomic absorption method was used.

Example 1: Sulfuric acid solution immersion test of EFB original product An EFB original product cut to about 10 g per piece was used as a sample, and 100 g of the sample was immersed in 1000 g of sulfuric acid solution at room temperature without stirring for 6 days. The sulfuric acid solution concentration was 0.69 g per 100 g of the sample. This amount corresponds to 0.5 equivalent of potassium contained in the sample, and the pH at the start of immersion was 2.5. Thereafter, sulfuric acid was added so that the pH of the sulfuric acid solution became 2.5 after one day.

  After immersion for 6 days, a sample was collected, 10 times the amount of pure water was added, and the mixture was stirred with a stirrer at 600 rpm for 3 hours. Then, the sample was collected, the adhering water was removed with pure water, dried and pulverized, and the potassium analysis was performed. For potassium analysis, wet decomposition-flame atomic absorption method was used, and the pH of the sulfuric acid solution was measured by the glass electrode method of JIS K 0102 12.1.

Example 2: Sulfuric acid solution immersion test of EFB prototype The same EFB prototype as in Example 1 was used as a sample, and 100 g of the sample was immersed in 1000 g of sulfuric acid solution at room temperature for 1 day without stirring. The sulfuric acid solution concentration was 2.07 g per 100 g sample. This amount corresponded to 1.5 equivalents of potassium contained in the sample, and the pH at the start of immersion was 1.8. No sulfuric acid was added. After the immersion for 1 day, it processed similarly to Example 1 and analyzed.

Example 3: Sulfuric acid solution immersion test of EFB original product A test was performed in the same manner as in Example 2. However, the sulfuric acid solution concentration was 4.14 g per 100 g of the sample. This amount corresponds to 3.0 equivalents of potassium contained in the sample, and the pH at the start of immersion was 1.3.

Example 4: Sulfuric acid solution immersion test of EFB crushed product Palm EFB original product was crushed and classified with a sieve to obtain 1-5 mm EFB crushed product. Using this as a sample, the test was performed in the same manner as in Example 1. However, no sulfuric acid was added during the 6-day immersion. After 6 days of immersion, the same treatment as in Example 1 was performed for analysis.

Comparative Example 1: Pure water immersion test of EFB crushed product In the same manner as the sulfuric acid solution immersion test of Example 4, an immersion test was performed using pure water instead of the sulfuric acid solution. In this test, a 1-day pure water immersion test and a 3-day pure water immersion test were also performed.

  The results of Examples 1 to 4 and Comparative Example 1 are shown in Table 1.

  As shown in Table 1, even if the palm palm EFB is the original product, when the sulfuric acid solution concentration is 1.5 equivalents or more of potassium contained in the sample, the potassium concentration in the remaining EFB is 560 mg / day after immersion for 1 day. kg-dry base, potassium removal rate was 94.9% or more. When the crushed product is used as a sample and immersed in a sulfuric acid solution for 6 days, the potassium concentration in the residual EFB is less than 100 mg / kg-dry base even if the sulfuric acid solution concentration is 0.5 equivalent of potassium contained in the sample. (70 mg / kg-dry base: reference value), and the removal rate of potassium was 99.4% or more. In addition, the detection lower limit of the wet decomposition-flame atomic absorption method used for the analysis of potassium is 100 mg / kg.

  Regarding the relationship between the sample form and the potassium removal rate, the pulverized product had a higher potassium removal rate than the original product.

  In the immersion test using pure water of Comparative Example 1, a pulverized product was used as a sample. Even after 6 days of immersion, the potassium concentration in the sample was 1700 mg / kg-dry base, and the potassium removal rate was 84. .5%.

  Looking at the potassium removal rate in relation to the pH of the sulfuric acid solution, the lower the pH at the start of immersion and the lower the pH at the end of immersion, the higher the potassium removal rate. This is consistent with the fact that the potassium removal rate was low in the immersion test using pure water.

  The pH of the sulfuric acid solution is affected by the potash that adheres to the sample. It should be noted that the pH may not decrease as expected when there is a large amount of alkali attached to the sample. In addition, when there is a large amount of alkali adhering to the sample, it is preferable to remove the adhering alkali before dipping the sulfuric acid solution in terms of suppressing the consumption of the sulfuric acid solution. In the sulfuric acid solution immersion test of this test, the change in pH before and after immersion was less compared with the original product because the crushed product was washed with water prior to crushing. Is estimated to have been removed.

  Table 2 shows industrial analysis results of residual EFB after the sulfuric acid solution immersion test of Example 2. It can be seen that the contents of chlorine and sodium are both less than 100 mg / kg-dry base, and the remaining amount is small compared to potassium. Also, the lower heating value is about 19000 kJ / kg-dry base, and it can be seen that the heating value is sufficient even after immersion in the sulfuric acid solution.

  FIG. 5 is photographs of samples before and after the sulfuric acid solution immersion test of Examples 1 to 3 of the present invention. As can be seen from this figure, there was no change in appearance before and after immersion. In Example 4 in which a pulverized product was used as a sample, the sample was visually observed, and no change was observed in the appearance before and after immersion. In Comparative Example 1, no change was observed in the appearance of the sample before and after immersion.

Comparative Example 2: Water-washing test of EFB original solid product A water-washing test was performed in the following manner, using the palm palm EFB original product as a sample. 2000 g of pure water was added to 200 g of the sample, and the mixture was stirred with a stirrer at room temperature for 1.5 hours. Then, it filtered and isolate | separated into the sample and water, and analyzed the electrical conductivity and potassium ion concentration of the filtrate. An electric conductivity meter was used for measuring the electric conductivity, and a potassium ion analyzer and an ion chromatogram method were used for the potassium ion concentration.

  The above hydration, stirring, and filtration operations were performed as a single water washing operation, and three water washing operations were repeated. After the three water washing operations, potassium in the sample was analyzed. Analysis was performed by wet decomposition-flame atomic absorption. The stirring time per washing operation was determined by determining the time required to reach saturation from the change over time in the electrical conductivity and potassium ion concentration of the filtrate in the absorbency confirmation test conducted separately.

  The results of washing with water are shown in Table 3. Of the potassium removal rates in Table 3, the results of water analysis are calculated from the potassium ion concentration and the filtrate amount in the filtrate. The potassium concentration in the sample of the palm palm EFB original product after washing with water was 5700 mg / kg-dry base, and the potassium removal rate was 36.7%.

Comparative Example 3: Washing test of EFB crushed product For palm palm EFB crushed product, 3000 g of pure water was added to 300 g of palm palm EFB crushed product, and a water washing test was performed in the same manner as the EFB original product of Comparative Example 2. The potassium concentration in the sample after washing with water was 4800 mg / kg-dry base, the removal rate of potassium was 56.4%, and potassium was not sufficiently removed.

Comparative Example 4: Washing test of ground pulverized griricidia A washing test was carried out in the following manner using Gliricidia, which is a leguminous tree of Sri Lanka, as an object to be cleaned. The grillicidia log was roughly pulverized to a size of about 1 to 5 mm, and the pulverized product was dried and washed with water. The washing conditions were a stirrer, a washing ratio (water / pulverized dry product) of 10 times, and stirring at room temperature for 2 hours. The analysis of potassium and sodium was performed by wet analysis-flame atomic absorption method, and the analysis of total chlorine was performed by bomb combustion-ion chromatography.

Comparative Example 5: Water-washing test of grillicidia semi-carbide Grindidia log was coarsely pulverized to a size of about 1 to 5 mm, the pulverized product was dried and dry-distilled to obtain semi-carbide. The semi-carbonizing condition was set to 290 ° C. with a heating time of 1 hour while supplying nitrogen gas into the furnace at 500 mL / min. Thereafter, it was washed with water in the same manner as in Comparative Example 4.

Comparative Example 6: Water washing test of pulverized product of Grilicidia semicarbide After obtaining a semicarbide in the same manner as in Comparative Example 5, the semicarbide was pulverized, and then washed in the same manner as in Comparative Example 4.

Comparative Example 7: Warm water washing test of pulverized product of glycyricidia semi-carbide After the water washing test of Comparative Example 6, it was further washed with hot water at 50 ° C.

  The results of Comparative Examples 4 to 7 are shown in Table 4. As shown in Comparative Example 4, sodium and chlorine could be reduced in concentration simply by washing the crushed raw wood with water. In contrast, potassium could not be removed sufficiently by washing with water. Further, when semi-carbonized, potassium and sodium were concentrated (see Comparative Examples 4 and 5), and the removal rate of semi-carbide was worse than washing with water as it was.

1, 2 Cleaning device 5 Biomass 6 Acid solution 7 Water 11 Container 12 Net bag 13, 14 Acid tank 15, 16 Water tank 17, 18 Circulation pump 21 Rope with hook

Claims (4)

  A method for washing biomass, comprising a dipping step of immersing raw biomass in an acidic solution and removing alkali metals contained in the biomass.   The acidic solution has a pH at the end of the dipping step of 4.0 or less, and a pH at the start of the dipping step of 2.5 or less, preferably 2.0 or less, more preferably 1.8 or less. The method for cleaning biomass according to claim 1, wherein:   The method for washing biomass according to claim 1 or 2, wherein the acidic solution is a sulfuric acid solution.   A method for producing a solid fuel, comprising a semi-carbonization / carbonization step of semi-carbonizing or carbonizing a biomass washed product obtained by the method for cleaning biomass according to any one of claims 1 to 3.