ISO 21656:2021 pdf download – Solid recovered fuels — Determination of ash content.
Remove the dish with its content from the furnace. Allow the dish and its content to cool on a thick metal plate for 5 min to 10 min and then transfer to a desiccator without desiccant and allow to cool to ambient temperature. Weigh the ash and the dish to the nearest 0,1 mg as soon as ambient temperature is reached and record the mass. Calculate the ash content of the sample as detailed in Clause 8. If there is any doubt of complete incineration (for instance presence of soot at visual inspection), then add droplets of water or ammonium nitrate to the sample before it is reloaded into the cold furnace and reheated to (550 ± 10) °C for a period of further 30 min until the change in mass is lower than 0,2 mg. Automatic equipment may be used if the method is validated with biomass reference samples of an adequate biomass type. This equipment shall fulfil all the requirements given in this clause regarding sample size, heating procedure, atmosphere, temperatures and weighing accuracy. Deviations from this paragraph shall be reported and justified. 7.3 Method B – ash content at 815 °C Heat the empty dish (5.1) in the furnace (5.2) to (815 ± 10) °C for at least 60 min. Allow the dish to cool down in a desiccator. After the dish is cooled, weigh it to the nearest 0,1 mg and record the mass. Place about 1 g of the general analysis sample on the bottom of the dish and spread in an even layer over the bottom surface. Weigh the dish plus the sample to the nearest 0,1 mg and record the mass. If the general analysis sample is oven-dried, both the dish and the sample shall be dried at (105 ± 10) °C as a precautionary measure against water absorption and then weighed. Place the loaded dish in the cold furnace. Heat the sample in the furnace according to the following heating routine: a) raise the furnace temperature evenly to (250 ± 10) °C over a period of 50 min (i.e. a rise of 5 °C/ min). Maintain at this temperature level for 60 min to allow the volatiles to leave the sample before ignition;