This document specifies methods for the determination of major and minor element concentrations in solid recovered fuels after digestion by the use of different acid mixtures and by addition of a fluxing agent for solid recovered fuel (SRF) ash.
a)       Method A: Microwave assisted digestion with hydrochloric, nitric and hydrofluoric acid mixture (6 ml HCl; 2 ml HNO3; 2 ml HF) followed by boric acid complexation;
b)       Method AT: Microwave assisted digestion with hydrochloric, nitric and tetrafluoroboric acid mixture (6 ml HCl; 2 ml HNO3; 4 ml HBF4);
c)        Method B: Microwave assisted digestion with hydrochloric, nitric and hydrofluoric acid mixture (0,5 ml HCl; 6 ml HNO3; 1 ml HF) followed by boric acid complexation;
d)       Method BT: Microwave assisted digestion with hydrochloric, nitric and tetrafluoroboric acid mixture (0,5 ml HCl; 6 ml HNO3; 2 ml HBF4);
e)       Method C: Microwave assisted digestion with nitric acid, hydrogen peroxide and hydrofluoric acid mixture (2,5 ml H2O2; 5 ml HNO3; 0,4 ml HF) and optional boric acid complexation;
f)         Method CT: Microwave assisted digestion with nitric acid, hydrogen peroxide and tetrafluoroboric acid mixture (2,5 ml H2O2; 5 ml HNO3; 0,8 ml HBF4);
g)       Method D: Digestion of the ashed SRF sample with fluxing agent lithium metaborate in an oven at 1 050 °C.
This document is applicable for the following major and minor/trace elements:
—     Major elements: aluminium (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), sodium (Na), phosphorus (P), sulfur (S), silicon (Si) and titanium (Ti).
—     Minor/trace elements: arsenic (As), barium (Ba), beryllium (Be), cadmium (Cd), cobalt (Co), chromium (Cr), copper (Cu), mercury (Hg), molybdenum (Mo), manganese (Mn), nickel (Ni), lead (Pb), antimony (Sb), selenium (Se), tin (Sn), thallium (Tl), vanadium (V) and zinc (Zn).
Method A is applicable for general use for SRF and ashed SRFs, but the amount of the test portion can be very low in case of high concentration of organic matter. Method AT can be used if an alternative to HF is necessary.
Method B with a higher volume of nitric acid is applicable for SRFs with high organic matter (e.g. suitable for high plastic content) that can be difficult to digest with less nitric acid or as a substitute for method A if appropriate equipment is not available. Method BT can be used if an alternative to HF is necessary.
Method C with combination of nitric acid and hydrogen peroxide and addition of hydrofluoric acid is applicable for wood based SRFs (e.g. demolition wood) or when there is a need for comparability to solid biofuel standards. Method CT can be used if an alternative to HF is necessary.
Method D is specifically applicable for determination of major elements in ashed SRF samples.
XRF can be used for the analysis of major elements (Al, Ca, Fe, K, Mg, Na, P, S, Si, Ti) after ashing (815 °C) of the samples and several major and minor/trace elements in SRF can be analysed by XRF after suitable calibration provided that the concentration levels are above instrumental detection limits of the XRF instrumentation and after proper preliminary testing and validation.
Digestion methods with HF and subsequent boric acid complexation or application of method D are applicable for determination of Si and Ti (better digestion efficiency).
Alternative digestion methods can be applied, if their performance is proved to be comparable with those of the methods described in this document.