【木屑顆粒機(jī)】<木屑顆粒規(guī)格和方法比較>

木屑顆粒規(guī)格和方法比較 

Pellet Specification & Method Comparisons

雖然PFI和ISO標(biāo)準(zhǔn)在許多方面看起來非常相似，但重要的是要注意兩者在規(guī)格和參考測試方法中的微妙差異。

While the PFI and ISO standards seem very similar in many ways, it is important to note the often subtle differences in the specifications and the referenced test methods, as PFI and ISO are not always comparable.

以下將就規(guī)格和方法兩方面對PFI標(biāo)準(zhǔn)和ISO 17225-2標(biāo)準(zhǔn)進(jìn)行比較。

Recently, I was asked to compare the methods and specifications referenced in the PFI standards with the seemingly similar ISO 17225-2 standard.

請記住，PFI標(biāo)準(zhǔn)是為北美木屑顆粒行業(yè)開發(fā)的，而在大多數(shù)情況下，新發(fā)布的ISO標(biāo)準(zhǔn)非常類似于以前的ENplus標(biāo)準(zhǔn)，這些標(biāo)準(zhǔn)都是服務(wù)于歐洲木屑顆粒市場的。ENplus和CANplus標(biāo)準(zhǔn)現(xiàn)在參考質(zhì)量等級規(guī)格A1、A2和B級，正如ISO 17225-2中所述的，但生產(chǎn)商主要生產(chǎn)“A1級”。

Bear in mind that the PFI standards were developed for the North American wood pellet industry, while in most cases, the newly published ISO standards closely resemble former EN standards, which were written for the European markets. ENplus and CANplus now reference the specifications for quality classes A1, A2 and B, as outlined in ISO 17225-2, but producers primarily manufacture “A1 grade.”

此外，雖然PFI標(biāo)準(zhǔn)包括高級、標(biāo)準(zhǔn)和通用等級標(biāo)準(zhǔn)，但絕大多數(shù)生產(chǎn)者制造高級等級。本文將PFI的高級等級與ISO 17225-2 A1等級的要求進(jìn)行比較。

Also, while the PFI standards provide criteria for premium, standard and utility grades, the vast majority of producers manufacture premium grade. This exercise compares the requirements of PFI’s premium grade with ISO 17225-2 A1 grade.

PFI標(biāo)準(zhǔn)允許40-48磅/立方英尺的體積密度范圍，而ISO 17225-2涉及600-750千克（kg）/每立方米范圍，（37.5至46.8磅/立方英尺）。測試方法的不同之處在于它們使用不同尺寸的容器、不同的壓縮方法和不同的澆注高度。除了這些差異之外，這兩種方法具有大程度的可變性，這取決于個(gè)人技術(shù)。盡管存在這些差異和固有的可變性，這兩種方法似乎產(chǎn)生類似的結(jié)果。

PFI specifications allow a bulk density range of 40 to 48 pounds per cubic foot, while ISO 17225-2 references a range of 600 to 750 kilograms (kg) per cubic meter. (37.5 to 46.8 pounds per cubic foot). The test methods are different in that they use different-sized containers, different methods of compaction and different pour heights. In addition to these differences, both methods inherently have a large degree of variability as a result of the test being dependent on individual technique. Despite all of these differences and the inherent variability, the two methods do seem to generate similar results.

PFI的直徑范圍是0.230-0.285英寸（5.84-7.24毫米（mm）），這是基于美國生產(chǎn)商主要使用四分之一英寸模具和一些稍大的模具。ISO 17225-2要求生產(chǎn)者使用6或8mm，每個(gè)允許±1mm的公差，即允許5至9mm（0.197至0.354英寸）范圍，假定6mm直徑最接近常規(guī)的四分之一英寸（6.35mm ）模具尺寸，則預(yù)期生產(chǎn)者將使用6mm。不確定8mm直徑產(chǎn)品會(huì)如何影響爐具性能。兩種測試方法的平均值的直徑都是使用卡尺來測量的。

PFI’s diameter range is 0.230 to 0.285 inches (5.84 to 7.24 millimeters (mm). This is with the understanding that U.S. producers predominantly use a one-quarter-inch die and some slightly larger die sizes. ISO 17225-2 requires that producers declare 6 or 8 mm, each with a tolerance plus or minus 1 mm, allowing for a potential range of 5 to 9 mm (0.197 to 0.354 inches).  Given that the 6 mm diameter most closely resembles the customary one-quarter-inch (6.35 mm) die size, it would be expected that producers would declare 6 mm. It is uncertain as to how the 8 mm diameter product would affect stove performance. Both test methods use calipers to measure the diameter where the mean value is reported.

至于耐久性，PFI方法遵循滾筒方法，其中外形尺寸為12英寸×12英寸×5.5英寸（305mm×305mm×140mm）。ISO方法使用類似略小的滾筒（300mm×300mm×120mm）。沒有發(fā)現(xiàn)尺寸的差異導(dǎo)致測試結(jié)果的顯著差異。

For durability, the PFI method follows the tumbler method, where the chamber dimensions are 12 inches by 12 inches by 5.5 inches (305 mm by 305 mm by 140 mm). The ISO method uses a similar tumbler that is just slightly smaller (300 mm by 300 mm by 120 mm). I have not found the differences in the box dimensions to cause a significant difference in test results, but in theory, the slightly larger box could suggest a slightly more aggressive test for the PFI method.

PFI將細(xì)粒定義為可通過八分之一英寸篩網(wǎng)（3.175-mm方孔）的材料。對于ISO 17225-2，細(xì)粒定義為通過3.15 mm圓孔篩網(wǎng)的材料。即使尺寸3.175和3.15看起來類似，因?yàn)镻FI的是方形孔，并且ISO的是圓形孔，孔徑尺寸的差異約30％。因此，PFI測試將較大部分的材料分類為細(xì)粒，盡管對ISO具有可比的細(xì)粒要求（對于袋裝材料，兩者的參考細(xì)度限值為0.5％）。此外，當(dāng)通過PFI方法測試時(shí)，導(dǎo)致耐久性測試結(jié)果降低約0.7。

PFI defines fines as material passing through a one-eighth-inch wire mesh screen (3.175-mm square hole). For ISO 17225-2, fines are defined as material passing through a 3.15-mm round hole screen. Even though the screen dimensions 3.175 and 3.15 seem similar, because the PFI screen has square holes and the ISO screen has round holes, the difference in aperture size is about 30 percent. As such, the PFI test classifies a larger portion of the material as fines making it harder to pass the PFI fines test, despite having a comparable fines requirement for ISO (both reference a fines limit of 0.5 percent for bagged material). In addition, this causes the durability test result to be approximately 0.7 lower when tested via the PFI method.

對于灰分含量，PFI和ISO使用相當(dāng)類似的灰化溫度，PFI為580-600攝氏度，ISO為550℃。我沒有看到這些溫度之間的顯著差異，我認(rèn)為這兩種方法提供可比的結(jié)果。PFI灰分限制為1％，ISO 17225-2灰分限制為0.7％。

For ash content, both PFI and ISO use fairly similar temperatures for ashing, 580 to 600 degrees Celsius for PFI, and 550 C for ISO. I have not seen a significant difference between these temperatures, and I consider these two methods to deliver comparable results. The PFI limit for ash is 1 percent, and the ISO 17225-2 limit for ash is 0.7 percent.

關(guān)于長度，PFI不允許超過1％長于1.5英寸（38.1mm），而ISO不允許超過1％長于40mm（1.57英寸），并且沒有長于45mm的顆粒。當(dāng)比較38.1mm 和40mm時(shí)，PFI測試更嚴(yán)格，但是，ISO標(biāo)準(zhǔn)規(guī)定不允許顆粒超過45mm，這方面來說ISO更嚴(yán)格。對于測試方法，PFI測試更徹底，因?yàn)樵?.5磅（1.134克）的最小樣品尺寸上進(jìn)行測試，而ISO測試在30至40克下進(jìn)行。

Regarding length, PFI does not allow more than 1 percent to be longer than 1.5 inches (38.1 mm), while ISO does not allow more than 1 percent to be longer than 40 mm (1.57 inches) and no pellets longer than 45 mm. When comparing 38.1 mm 40 mm, the PFI test is more rigorous, however, the ISO specification that no pellet can be longer than 45 mm can make the ISO specifications more rigorous. For the test method, the PFI test is more thorough, in that the test is performed on a minimum sample size of 2.5 pounds (1,134 grams) while the ISO test is performed on 30 to 40 grams.

PFI和ISO使用熱量計(jì)方法來確定熱值，并且兩個(gè)參考測試結(jié)果直接來自儀器的。然而，對于ISO 17225-2，能量含量的規(guī)定限度表示凈熱值，也稱為較低熱值。 對于PFI，熱值表示為總熱值或更高的熱值（HHV）。這些參數(shù)不能直接比較。ISO規(guī)定A1等級顆粒需要大于或等于4.6千瓦時(shí)/ kg（相當(dāng)于7119Btu /磅）。PFI標(biāo)準(zhǔn)要求生產(chǎn)者公開收到的最低HHV。

PFI and ISO use calorimeter methods for determining the heating value, and both referenced tests yield comparable results direct from the instrument. For ISO 17225-2, however, the specified limit for energy content is expressed as the net calorific value, also referred to as lower heating value. For PFI, the heating value is expressed as the gross calorific value, or higher heating value (HHV). These parameters are not directly comparable. ISO provides a limit that the A1 pellets need to be greater than or equal to 4.6 kilowatt-hour per kg (equivalent to 7119 Btu per pound). The PFI Standard requires the producer to disclose the minimum HHV as-received.

ISO方法主要用氯離子色譜法作為主要方法，但允許幾種直接分析技術(shù)。PFI列出了幾種接受的方法。它們的檢測范圍和所需的儀器都不同。PFI對氯的限值為300毫克（mg）/每千克（kg），ISO要求為200mg/kg。

The ISO method for chlorine references ion chromatography as the primary method, but has language for allowing several direct analysis techniques. PFI lists several accepted methods. All differ in their detection limits and instrumentation required. PFI’s limit for chlorine is 300 milligrams (mg), per kilogram (kg) and the ISO requirement is 200 mg per kg.

PFI目前沒有在其標(biāo)準(zhǔn)中列出金屬限制，并且沒有指定測試方法。ISO對八種金屬有限制，并參考了一種用于分析金屬的ISO測試方法。ISO 17225-2還列出了PFI標(biāo)準(zhǔn)中沒有的幾個(gè)附加參數(shù)的要求，包括變形溫度，氮和硫。

PFI does not currently have metals listed in its standard, and no test method is specified. ISO has limits for eight metals, and references an ISO test method for analyzing metals. ISO 17225-2 also lists requirements for several additional parameters not included in the PFI standards, including deformation temperature, nitrogen and sulfur. 

雖然PFI和ISO標(biāo)準(zhǔn)在許多方面看起來非常相似，但重要的是要注意兩者在規(guī)格和參考測試方法中的微妙差異。

While the PFI and ISO standards seem very similar in many ways, it is important to note the often subtle differences in the specifications and the referenced test methods, as PFI and ISO are not always comparable.

來源：Biomass Magazine

Author：Chris Wiberg