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发布日期:2016-08-02 作者: 点击:



Pellet Specification & Method Comparisons


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.

以下将就规格和方法两方面对PFI标准和ISO 17225-2标准进行比较。

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

请记住,PFI标准是为北美木屑颗粒行业开发的,而在大多数情况下,新发布的ISO标准非常类似于以前的ENplus标准,这些标准都是服务于欧洲木屑颗粒市场的。ENplus和CANplus标准现在参考质量等级规格A1、A2和B级,正如ISO 17225-2中所述的,但生产商主要生产“A1级”。

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,虽然PFI标准包括高级、标准和通用等级标准,但绝大多数生产者制造高级等级。本文将PFI的高级等级与ISO 17225-2 A1等级的要求进行比较。

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标准允许40-48磅/立方英尺的体积密度范围,而ISO 17225-2涉及600-750千克(kg)/每立方米范围,(37.5至46.8磅/立方英尺)。测试方法的不同之处在于它们使用不同尺寸的容器、不同的压缩方法和不同的浇注高度。除了这些差异之外,这两种方法具有大程度的可变性,这取决于个人技术。尽管存在这些差异和固有的可变性,这两种方法似乎产生类似的结果。

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的直径范围是0.230-0.285英寸(5.84-7.24毫米(mm)),这是基于美国生产商主要使用四分之一英寸模具和一些稍大的模具。ISO 17225-2要求生产者使用6或8mm,每个允许±1mm的公差,即允许5至9mm(0.197至0.354英寸)范围,假定6mm直径最接近常规的四分之一英寸(6.35mm )模具尺寸,则预期生产者将使用6mm。不确定8mm直径产品会如何影响炉具性能。两种测试方法的平均值的直径都是使用卡尺来测量的。

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.


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将细粒定义为可通过八分之一英寸筛网(3.175-mm方孔)的材料。对于ISO 17225-2,细粒定义为通过3.15 mm圆孔筛网的材料。即使尺寸3.175和3.15看起来类似,因为PFI的是方形孔,并且ISO的是圆形孔,孔径尺寸的差异约30%。因此,PFI测试将较大部分的材料分类为细粒,尽管对ISO具有可比的细粒要求(对于袋装材料,两者的参考细度限值为0.5%)。此外,当通过PFI方法测试时,导致耐久性测试结果降低约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.

对于灰分含量,PFI和ISO使用相当类似的灰化温度,PFI为580-600摄氏度,ISO为550℃。我没有看到这些温度之间的显着差异,我认为这两种方法提供可比的结果。PFI灰分限制为1%,ISO 17225-2灰分限制为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.

关于长度,PFI不允许超过1%长于1.5英寸(38.1mm),而ISO不允许超过1%长于40mm(1.57英寸),并且没有长于45mm的颗粒。当比较38.1mm 和40mm时,PFI测试更严格,但是,ISO标准规定不允许颗粒超过45mm,这方面来说ISO更严格。对于测试方法,PFI测试更彻底,因为在2.5磅(1.134克)的最小样品尺寸上进行测试,而ISO测试在30至40克下进行。

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使用热量计方法来确定热值,并且两个参考测试结果直接来自仪器的。然而,对于ISO 17225-2,能量含量的规定限度表示净热值,也称为较低热值。 对于PFI,热值表示为总热值或更高的热值(HHV)。这些参数不能直接比较。ISO规定A1等级颗粒需要大于或等于4.6千瓦时/ kg(相当于7119Btu /磅)。PFI标准要求生产者公开收到的最低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.


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目前没有在其标准中列出金属限制,并且没有指定测试方法。ISO对八种金属有限制,并参考了一种用于分析金属的ISO测试方法。ISO 17225-2还列出了PFI标准中没有的几个附加参数的要求,包括变形温度,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. 



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.

来源:Biomass Magazine

Author:Chris Wiberg