Quality evaluation method for fuel pellets made of EFB

Abstract

This provides a quality evaluation method that allows for the estimation, or evaluation, of the chlorine concentration of fuel pellets within a predetermined concentration range at a site where fuel pellets are manufactured from EFB (Energy Fiber Filled). [Solution] This is a quality evaluation method for evaluating the chlorine concentration in fuel pellets manufactured using EFB as a raw material. The quality evaluation method comprises a potassium concentration estimation step for estimating the potassium concentration in the fuel pellets, and a chlorine concentration evaluation step for evaluating the chlorine concentration. Based on the estimated potassium concentration, the chlorine concentration evaluation step evaluates that when the potassium concentration is 4,000 ppm or less, the chlorine concentration is less than or equal to the potassium concentration multiplied by 0.086.

Description

Technical Field

[0001] The present invention relates to a quality evaluation method for evaluating the quality of fuel pellets manufactured from palm empty fruit bunches, that is, EFB (Empty Fruit Bunch).

Background Art

[0002] The fruits of the palm tree are contained in large numbers in the bunch-shaped palm fruit bunches, and palm oil is obtained by squeezing the fruits separated from the palm fruit bunches. The remaining bunch after the fruits are removed, that is, EFB (palm empty fruit bunch), is generated in large quantities in palm oil mills and has been conventionally disposed of, but in recent years, fuel pellets have been manufactured and used therefrom.

[0003] By the way, for wood pellet fuels, the International Organization for Standardization, the European Committee for Standardization, etc. have established standards regarding quality. This is because a certain quality is required to be able to use them safely and appropriately when used in boilers and the like. For example, according to the International Organization for Standardization "ISO 17225-1(2021)", in the highest quality category A1, for example, it is stipulated that the ash melting behavior, that is, the ash softening point temperature (DT) is 1,200 °C or higher, and the chlorine (Cl) concentration is 200 ppm or lower.

[0004] Fuel pellets made from EFB (Empty Fuel Cellulose) should also be supplied in accordance with these standards to ensure safe use in boilers. However, EFB contains a relatively large amount of potassium, a low-melting-point metal. While these standards do not specify potassium concentration, if the potassium concentration is high, combustion in boilers can cause clinker to form in the fluidized bed, leading to fouling and slugging, where combustion ash solidifies and adheres to the furnace and heating pipes. This is because potassium lowers the ash softening point (DT). Therefore, when manufacturing fuel pellets from EFB, as described in Patent Document 1, for example, the EFB is crushed and immersed in washing water to reduce the potassium concentration before being molded into pellets.

[0005] The ash softening point (DT) of fuel pellets made of EFB (Energy Fiber Burst) is measured by providing a sample of the fuel pellets to a specialized analytical laboratory. However, this process takes a long time, affecting the efficiency of fuel pellet manufacturing. Incidentally, the ash softening point (DT) is correlated with potassium concentration. Therefore, at the fuel pellet manufacturing site, a relatively simple testing device is used to measure the potassium concentration of the fuel pellets, and this is used to estimate whether the ash softening point (DT) meets the standard. This is then confirmed by the test results received later from the analytical laboratory. Even if the ash softening point (DT) does not meet the standard for category A1, clinker formation can be suppressed, for example, by co-firing the fuel pellets with other fuels at a predetermined co-firing ratio. However, even in this case, improvement of the ash softening point (DT) is necessary, and it is required to control the potassium concentration within an appropriate range. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2025-24612 [Overview of the project] [Problems that the invention aims to solve]

[0007] While the final quality confirmation of fuel pellets made from EFB (Energy Fiber Burst) requires the results of tests conducted by specialized analytical institutions, the ash softening point (DT) can be estimated at the manufacturing site by measuring the potassium concentration of the fuel pellets. Therefore, this does not affect manufacturing efficiency. However, there are other issues that need to be addressed. Specifically, there is no simple means to measure at the manufacturing site whether the chlorine concentration in EFB fuel pellets meets the standard. As mentioned above, the standard for chlorine concentration is, for example, 200 ppm, which is a low concentration. As will be explained later, the concentration of substances contained in fuel pellets is measured by dissolving and immersing a predetermined amount of fuel pellets in a predetermined amount of solution, such as hot water. In other words, the concentration of the substance dissolved in the solution is measured with a testing device and calculated from this. The same procedure is followed for chlorine, but the chlorine concentration in the solution, such as hot water, is even lower than the chlorine concentration in the fuel pellets. As such, there is no simple means to measure such low concentrations. In other words, it is not easy to estimate at the manufacturing site whether the chlorine concentration in fuel pellets meets the standard. This presents a problem: fuel pellets must be manufactured without knowing whether or not they meet the standards regarding chlorine concentration.

[0008] The present invention aims to solve the above-mentioned problems and, specifically, to provide a quality evaluation method for fuel pellets made from EFB that allows for the estimation, or evaluation, of the chlorine concentration of fuel pellets within a predetermined concentration range at the site where fuel pellets are manufactured from EFB, thereby enabling easy evaluation of whether or not the chlorine concentration of fuel pellets meets the standards set by the International Organization for Standardization and other organizations. [Means for solving the problem]

[0009] The present invention is configured as a quality evaluation method for evaluating the chlorine concentration in fuel pellets manufactured using EFB as a raw material. The quality evaluation method comprises a potassium concentration estimation step for estimating the potassium concentration in the fuel pellets, and a chlorine concentration evaluation step for evaluating the chlorine concentration. The chlorine concentration evaluation step is performed based on the estimated potassium concentration. (1) When the potassium concentration is 4,000 ppm or less, the chlorine concentration is evaluated as being less than or equal to the potassium concentration multiplied by 0.086. [Effects of the Invention]

[0010] This invention makes it possible to evaluate the chlorine concentration of fuel pellets made of EFB (Earth-Fired Berry) by measuring the potassium concentration, which is relatively easy to measure, thereby making it difficult to measure the chlorine concentration in a simple manner. Specifically, it estimates the maximum possible chlorine concentration contained in the fuel pellets. Standards for wood pellet fuel established by organizations such as the International Organization for Standardization, the European Committee for Standardization, and Japan Pellet specify an upper limit for permissible chlorine concentration. For example, 300 ppm or less, or 200 ppm or less. By comparing such upper limits with the maximum chlorine concentration estimated by this invention, it is easy to determine whether or not the fuel pellets made of EFB meet the standards. [Brief explanation of the drawing]

[0011] [Figure 1] This flowchart shows the manufacturing process for producing fuel pellets from EFB (Energy Fiber Form). [Figure 2] This graph shows the relationship between potassium concentration and chlorine concentration in fuel pellets made of EFB (Energy Fiber). [Figure 3] This graph shows the relationship between potassium concentration and chlorine concentration in fuel pellets made of EFB (Energy Fiber). [Figure 4] This flowchart shows the procedure for evaluating the chlorine concentration in fuel pellets made of EFB. [Modes for carrying out the invention]

[0012] <This Embodiment> Hereinafter, embodiments of the present invention will be described. The method for evaluating the quality of fuel pellets according to this embodiment is a method for evaluating the chlorine content concentration of fuel pellets made of EFB. In fuel pellets made of EFB, the chlorine content concentration is often reduced by performing a cleaning process or the like, which will be described later. However, in this case, the chlorine content concentration becomes quite low, making it difficult to directly measure the concentration. Therefore, in the method for evaluating the quality of fuel pellets according to this embodiment, the chlorine content concentration is evaluated based on the concentration of other substances that are relatively easy to measure. Specifically, the potassium content concentration contained in the fuel pellets is used to evaluate the chlorine content concentration based on this.

[0013] <Manufacture of Fuel Pellets Made of EFB> First, the manufacturing method of fuel pellets made of EFB, which is the target of the method for evaluating the quality of fuel pellets according to this embodiment, will be described. As shown in FIG. 1, EFB is first pressed by a pressing process SS1. EFB is in a state where the fruits of palm oil have been removed, and this is heated and pressed. Then, moisture containing oil is separated. EFB oil is produced from the oil. For the pressed EFB, a water addition process SS2 is performed as necessary. That is, moisture is replenished. Note that after performing the pressing process SS1, it is also possible to move on to the crushing process SS3 without performing the water addition process SS2.

[0014] In the crushing process SS3, EFB is crushed. When it is crushed into crushed materials, potassium and chlorine contained in EFB are removed at a predetermined ratio together with moisture. When the water addition process SS2 is performed and moisture is replenished to EFB, the removal ratio becomes higher. Next, a cleaning process SS4 is performed. That is, the crushed materials of EFB are immersed in cleaning water. Then, potassium and chlorine contained in the crushed materials of EFB elute into the cleaning water. As a result, the potassium content concentration and the chlorine content concentration decrease.

[0015] Next, the dehydration and drying process SS5 is carried out. That is, the crushed material of the washed EFB is dehydrated. As a result, the potassium content concentration and chlorine content concentration are further reduced. The crushed material of the dehydrated EFB is dried. Finally, the forming process SS6 is carried out on the dried crushed material of EFB to produce fuel pellets. In the forming process SS6, the crushed material of EFB may be further crushed to be finer and then formed into fuel pellets. The forming of the fuel pellets can be carried out by well-known means such as a flat die, a ring die, etc. This concludes the description of the manufacturing method for producing fuel pellets from EFB.

[0016] <Relationship between Potassium Content Concentration and Chlorine Content Concentration in Fuel Pellets Composed of EFB> When producing fuel pellets composed of EFB, the potassium content concentration and chlorine content concentration in the fuel pellets vary depending on whether the washing process SS4 and the water addition process SS2 are carried out, that is, depending on the degree of washing. The inventors manufactured fuel pellets A to D by changing the manufacturing conditions, and entrusted these to a specialized analysis institution to measure the potassium content concentration and chlorine content concentration for each of the fuel pellets A to D. The results are shown below. ○ Fuel Pellet A Manufacturing conditions: The fuel pellets were manufactured without carrying out the water addition process SS2 or the washing process SS4, that is, without carrying out any washing or the like. Measurement results: Potassium content concentration 13,800 ppm, chlorine content concentration 2,300 ppm ○ Fuel Pellet B Manufacturing conditions: The fuel pellets were manufactured without carrying out the water addition process SS2 and carrying out the washing process SS4. That is, the degree of washing was set at a medium level for manufacturing. Measurement results: Potassium content concentration 3,760 ppm, chlorine content concentration 300 ppm ○ Fuel Pellet C Manufacturing conditions: The fuel pellets were manufactured by carrying out the water addition process SS2 and the washing process SS4. That is, the degree of washing was set at a slightly higher level for manufacturing. Measurement results: Potassium content concentration 3,320 ppm, chlorine content concentration 200 ppm ○ Fuel Pellet D Manufacturing conditions: Fuel pellets were manufactured by performing the water addition step SS2 and the cleaning step SS4. However, in the cleaning step SS4, a large amount of cleaning water was used. That is, the pellets were manufactured with a high level of cleaning. Measurement results: Potassium content concentration 2,130 ppm, chlorine content concentration 100 ppm

[0017] In the graph of FIG. 2, the horizontal axis represents the potassium content concentration and the vertical axis represents the chlorine content concentration, and for each of the fuel pellets A to D, they are shown as points A to D. Further, a graph 1 showing the relationship between the potassium content concentration and the chlorine content concentration was obtained from these points A to D. FIG. 3 shows an enlarged view of the low-concentration range of graph 1.

[0018] The inventors obtained two findings from graph 1. The first finding is that in fuel pellets made of EFB, if the potassium content concentration is known, the chlorine content concentration can be estimated with a certain degree of accuracy. That is, even if the chlorine content concentration cannot be directly measured, if the potassium content concentration can be measured or estimated, it becomes possible to evaluate the chlorine content concentration based on the potassium content concentration. The second finding is that the potassium content concentration and the chlorine content concentration do not follow a fixed ratio. More specifically, when the potassium content concentration decreases due to cleaning or the like, the chlorine content concentration decreases at an even greater rate. That is, it was found that chlorine elutes more easily than potassium due to cleaning or the like.

[0019] In EFB, both potassium and chlorine exist in an ionic state and are water-soluble, so it was predicted that their ease of elution would be equivalent. However, it was found that chlorine elutes more easily. The inventors speculate on the reason for this as follows: Potassium is a cation and is adsorbed to cellulose and hemicellulose, and also weakly bound to proteins and enzymes in cells. Cellulose and hemicellulose have OH and COOH groups, which are adsorbent to cations. Furthermore, many organic compounds in cells are negatively charged and take in many cations to neutralize them electrically. On the other hand, chlorine is an anion and basically exists as a free ion in water. Unlike potassium, it exists without adsorption or weak binding. Therefore, it is thought that chlorine elutes more easily than potassium.

[0020] <Method for evaluating the quality of fuel pellets> Based on the findings obtained, the inventors have established a fuel pellet quality evaluation method according to this embodiment. As shown in Figure 4, the fuel pellet quality evaluation method according to this embodiment first performs a potassium concentration estimation step S1 to estimate the potassium concentration contained in the fuel pellet made of EFB. Then, based on the potassium concentration estimated in step S1, a chlorine concentration evaluation step S2 is performed to evaluate the chlorine concentration. Steps S1 and S2 will be explained below.

[0021] <Potassium concentration estimation process> This is a process for estimating the potassium concentration in fuel pellets made of EFB. Any method can be used for estimation, but in this embodiment, it is done as follows. First, a predetermined mass is set aside from the fuel pellets to make test pellets. The test pellets are placed in a predetermined mass of hot water at 70°C or higher, more preferably 80°C or higher. The test pellets are loosened in the hot water and immersed for a predetermined time. During immersion, the temperature of the hot water is kept warm or heated as needed to prevent it from decreasing. After immersion, the potassium concentration in the hot water, i.e., the hot water potassium concentration, is measured. Any measuring instrument can be used for this measurement, but for example, a compact potassium ion meter LAQUAtwin-K-11 manufactured by HORIBA can be used. The measured hot water potassium concentration is multiplied by a predetermined elution coefficient to obtain the potassium concentration that was initially contained in the test pellets. In other words, the potassium concentration can be estimated.

[0022] Incidentally, the elution coefficient can be determined experimentally. Specifically, the experiment was conducted as follows: The specified mass of the test pellet was 10g, the specified mass of hot water was 10 times that amount (100g), and the specified immersion time was 10 minutes. Under these conditions, the potassium concentration of the hot water was measured and found to be 155ppm. Later, a specialized analytical laboratory was commissioned to analyze fuel pellets from the same manufacturing lot as the measured test pellet, and the potassium content was obtained at a later date to find it to be 2,730ppm. Dividing the potassium content by the potassium concentration of the hot water yielded an elution coefficient of 15.61. Under similar conditions, the experiment was repeated multiple times with fuel pellets from different manufacturing lots, measuring the potassium concentration of the hot water and obtaining the potassium content from a specialized analytical laboratory. The elution coefficient was calculated for each, and the result was within a 5% error range compared to the previously obtained elution coefficient of 15.61. In other words, as long as the specified mass of hot water is 10 times the specified mass of the test pellet and the specified immersion time is 10 minutes, an elution coefficient of 15.61 can be used. In other words, by immersing test pellets in hot water under these conditions and obtaining the potassium concentration of the hot water using a predetermined measuring instrument, the potassium concentration of the fuel pellets made of EFB can be estimated by multiplying this by the elution coefficient. The potassium concentration estimated in this way can be said to be estimated with an accuracy of within 5% error. It should be noted that the elution coefficient will naturally change if the ratio of the specified mass of test pellets to the specified mass of hot water changes, or if the specified immersion time changes.

[0023] <Chlorine concentration evaluation process> The chlorine concentration evaluation step according to this embodiment targets a low chlorine concentration range, for example, 350 ppm or less. This is because the standards already specified for wood pellets, as described above, specify chlorine concentrations of 300 ppm or less, 200 ppm or less, etc., making the low concentration range particularly important. The chlorine concentration evaluation step according to this embodiment estimates the maximum value of the contained chlorine concentration from the contained potassium concentration estimated by the potassium concentration estimation step. The contained chlorine concentration is then evaluated.

[0024] In the chlorine concentration evaluation process according to this embodiment, the basic evaluation method is as follows: That is, for fuel pellets made of EFB, (1) When the potassium concentration is 4,000 ppm or less, the chlorine concentration is evaluated as being less than or equal to the potassium concentration multiplied by 0.086. Figures 2 and 3 show Graph 11, which is a linear function passing through the origin with a slope of 0.086. The evaluation method in (1) above is based on the assumption that if the chlorine concentration of fuel pellets made of EFB could be accurately measured, it should be in the range below Graph 11. As is clear from Figures 2 and 3, Graph 1, which shows the relationship between potassium concentration and chlorine concentration, is located below Graph 11 when the potassium concentration is in the range of 4,000 ppm or less. From this, it can be said that this evaluation method is valid.

[0025] Incidentally, when the potassium concentration of fuel pellets made of EFB is 3,400 ppm, according to this evaluation method, the chlorine concentration can be evaluated as 3,400 ppm × 0.086 = 292.4 ppm or less, or 300 ppm or less. In the standards for wood pellets, ISO 17225-1:2014 and ISO 1725-2:2014, the chlorine concentration for category "B" of the standard is 300 ppm or less. Therefore, if the potassium concentration of fuel pellets made of EFB is 3,400 ppm or less, the chlorine concentration can be evaluated as 300 ppm or less, and at least in terms of chlorine concentration, the standard can be met.

[0026] In the chlorine concentration evaluation step according to this embodiment, the evaluation method (1) above may be adopted for the entire range of potassium content of 4,000 ppm or less, but when the potassium content is 3,000 ppm or less, the following evaluation method can be adopted. That is, for fuel pellets made of EFB, (2) When the potassium concentration is 3,000 ppm or less, the chlorine concentration shall be evaluated as being less than or equal to the potassium concentration multiplied by 0.066. Figures 2 and 3 show Graph 12, which is a linear function passing through the origin with a slope of 0.066. As is clear from Figures 2 and 3, Graph 1, which shows the relationship between potassium concentration and chlorine concentration, is located below Graph 12 when the potassium concentration is in the range of 3,000 ppm or less.

[0027] For fuel pellets made of EFB, if the potassium concentration is 3,000 ppm, this evaluation method allows us to assess the chlorine concentration as 3,000 ppm × 0.066 = 198 ppm or less, or 200 ppm or less. In the wood pellet standards ISO 17225-1:2014 and ISO 1725-2:2014, the chlorine concentration must be 200 ppm or less for categories "A1" and "A2" of the standard. Therefore, if the potassium concentration of fuel pellets made of EFB is 3,000 ppm or less, the chlorine concentration can be assessed as 200 ppm or less, thus meeting the standard at least in terms of chlorine concentration.

[0028] In the chlorine concentration evaluation step according to this embodiment, when the potassium content is 2,000 ppm or less, the following evaluation method can be adopted. That is, for fuel pellets made of EFB, (3) When the potassium concentration is 2,000 ppm or less, the chlorine concentration is evaluated as being less than or equal to the potassium concentration multiplied by 0.050. Figures 2 and 3 show Graph 13, which is a linear function passing through the origin with a slope of 0.050. As is clear from Figures 2 and 3, Graph 1, which shows the relationship between potassium concentration and chlorine concentration, is located below Graph 13 when the potassium concentration is in the range of 2,000 ppm or less. [Explanation of symbols]

[0029] 1. Graph showing the relationship between potassium concentration and chlorine concentration. 11. Graph with a slope of 0.086 12. Graph with a slope of 0.066 13. Graph with a slope of 0.050

Claims

1. A quality evaluation method for evaluating the chlorine concentration in fuel pellets manufactured using EFB as a raw material, The quality evaluation method comprises a potassium concentration estimation step for estimating the potassium concentration in the fuel pellet and a chlorine concentration evaluation step for evaluating the chlorine concentration. The chlorine concentration evaluation step is performed based on the estimated potassium concentration, (1) When the potassium concentration is 4,000 ppm or less, the chlorine concentration is less than or equal to the value obtained by multiplying the potassium concentration by 0.

086. A method for evaluating the quality of fuel pellets consisting of EFB, which are evaluated as follows.

2. The chlorine concentration evaluation step further includes: (2) When the potassium concentration is 3,000 ppm or less, the chlorine concentration is less than or equal to the value obtained by multiplying the potassium concentration by 0.

066. A method for evaluating the quality of fuel pellets made of EFB according to claim 1, which is evaluated as follows.

3. The chlorine concentration evaluation step further includes: (3) When the potassium concentration is 2,000 ppm or less, the chlorine concentration is less than or equal to the potassium concentration multiplied by 0.

050. A method for evaluating the quality of fuel pellets comprising EFB according to claim 1 or 2, which is evaluated as follows.

4. The potassium concentration estimation step comprises setting a predetermined amount of the fuel pellets to be used as test pellets, placing the test pellets in a predetermined amount of hot water to loosen them and immersing them for a predetermined time or longer, measuring the potassium concentration of the hot water, which is the potassium concentration in the hot water, and estimating the contained potassium concentration from the hot water potassium concentration, as described in claim 1 or 2, for the quality evaluation method of fuel pellets made of EFB.

5. The method for evaluating the quality of fuel pellets according to claim 4, wherein the hot water is 10 times the mass of the test pellet and is heated to 70°C or higher, and the specified time is 10 minutes.

6. The method for evaluating the quality of fuel pellets according to claim 4, wherein the estimation of the potassium content is calculated by multiplying the potassium concentration of the hot water by a predetermined elution coefficient to determine the potassium content that was initially contained in the test pellet.

7. A method for evaluating the quality of fuel pellets according to claim 1, wherein the manufacturing process for producing the fuel pellets from EFB includes at least a washing step of crushing the EFB and immersing it in washing water, the fuel pellets are manufactured so that the potassium concentration of the fuel pellets is 3,400 ppm or less, and the chlorine concentration of the fuel pellets is evaluated to be 300 ppm or less.

8. A method for evaluating the quality of fuel pellets according to claim 2, wherein the manufacturing process for producing the fuel pellets from EFB includes at least a washing step of crushing the EFB and immersing it in washing water, the fuel pellets are manufactured so that the potassium concentration of the fuel pellets is 3,000 ppm or less, and the chlorine concentration of the fuel pellets is evaluated to be 200 ppm or less.

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