ISO 21656-2021 pdf free download – Solid recovered fuels — Determination of ash content.
4Principle
The sample is heated in air atmosphere up to a temperature of (550±10) °C for Method A or(815±10)Cfor Method B under rigidly controlled conditions of time, sample mass and equipment specifications.The ash content is determined by calculation from the mass of the residue remaining after heating.NOTE Difference in the ash content if determined at 8150C compared to 550°C is explained by decompositionof carbonates formingCO, losses of volatile inorganic compounds (see also 3.5) and further oxidation of inorganiccompoundsll. In common standard practise, 550 °C is used for the determination of ash content in SRFs with ahigh content of biomass. 550 0C can also be used for major elemental determination (see also EN 15410l6l) andtrace elemental determination (see also EN 15411[Zl].
Automatic equipment (such as thermogravimetric analysers) may be used as long as the equipment isvalidated by parallel measurements to the reference method. T’he automatic equipment shall fulfil allthe requirements regarding sample size, heating procedure, temperature, atmosphere and weighingaccuracy. Deviations from this paragraph shall be reported and justified.
5 Apparatus
5.1 Dish, consisting of inert material such as porcelain, silica or platinum, with a depth from 10 mm to20 mm and such a size that the sample loading does not exceed 0,i g/cm2 bottom area.
5.2 Furnace, capable of maintaining a zone of uniform temperature at the levels required in Clause 7and to reach these levels in the specified heating rates. The ventilation rate through the furnace shouldbe such that no lack of oxygen arises during the heating procedure.
NOTE A ventilation rate from 5 air changes/min to 10 air changes/min are suitable.
5.3 Balance, capable of weighing the dish containing the sample to the nearest 0,1 mg.
5.4Desiccator, without desiccant.
NOTE The use of a desicator without desiccant is specified in lS0 1171 and emphasised here since ashesfrom solid recovered fuels are often more hygroscopic than coal ashes.
5.5Sieve, with an aperture size of s1 mm (according IS0 3310-1 or ISo 3310-2).5.6Container, sealed airtight.
6Sampling and sample preparation
6.1 General
The general analysis sample shall be taken and prepared in accordance with IlS0 21645 and lSO 21646.lt shall be ground to pass through a sieve with an aperture size of s1 mm.The general analysis sampleshall be received in the container (5.6). The general analysis sample shall either be oven-dried or itsmoisture content determined in accordance with lSo 21660-3.The general analysis sample shall bemixed carefully before weighing (see also Clause 7).
6.2Pre-drying
Pre-drying shall be performed according to ISO 21646.
Pre-drying of wet samples is carried out to minimize moisture loss in the subsequent sample-divisionprocesses, to facilitate the sample preparation processes,and to minimize biological activity. If it isnecessary to dry a sample by heating, it shall be dried in an oven at a temperature not exceeding thetemperature according iso 21646.
6.3Removed ash contributors (rac)
Coarse inert material (i.e. metals, glass, stones) can be removed from the pre-dried sample beforepreparation, in order to avoid damage to the preparation equipment.
Removed ash contributors (rac) from pre dried samples shall be considered as dry.
Arac is weighed separately,calculated as mass percent and added to the determined ash contentaccording to calculation in 8.2.
7Procedure
7.1General
A minimum of two determinations shall be carried out on the general analysis sample.
7.2Method A – ash content at 55o c
For the determination of the biomass fraction, use the temperature of 550 °C for all cases.ISO 21656 pdf download.