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Field characteristics of HCHO measurement method

pubblicazioni - Presentazione

Field characteristics of HCHO measurement method

La formaldeide (HCHO) è un composto estremamente diffuso in moltissime attività industriali e dal gennaio 2016 tale composto è stato ricatalogato come agente cancerogeno (H350) e mutagenico (H341) e ciò ne ha comportato una grossa limitazione nelle emissioni inquinanti, arrivando ai limiti attuali, che si attestano tra 2 e 5 mg/Nm3.Poiché questo composto era ritenuto non pericoloso fino a pochi anni fa, non si conducevano misure ambientale sistematiche e nel campo delle biomasse ad uso energetico, è presente nelle emissioni dei motori a scintilla utilizzati negli impianti di produzione del biogas.Poichè non esiste ancora un metodo europeo o internazionale validato per la sua determinazione nelle emissioni è stato iniziato il processo per la definizione di tale metodologia in ambito CEN (TC 624 WG 40). Nel lavoro si mostrano i principali risultati ottenuti.

Formaldehyde (CH2O) is a chemical compound extremely common in many industrial productions; is being used like as a solvent, for make-up products, preservative (also in foods as E240), and some years ago also in medications . Since January 2016, such compound has been re-classified as carcinogenic (H350) and mutagenic (H341), and this fact caused big limitations in emission limit of formaldehyde, down to the limit of 5 mg/Nm3.As Formaldehyde was thought to be not very dangerous up until few years ago, no European validated method for emissions control exists, as for such lack a new working item was initiated. In the field of biomasses, importance of formaldehyde is given by its presence in emissions from spark engines that burns biomethane.From a first examination of candidate methods, two analytical principles were selected: spectrophotometry (EPA 323) and HPLC (VDI 3862-2), using impingers with an absorption solution, as such technique is the most common also for other compounds.

The absorption solution tested were pure water and 0,01n H2SO4, like different addition protocols with DNPH (dinitrophenilhydrazine).From this first test trial, some important conclusions emerge:

• the presence of condensation in the sampling line can give rise to big measurement misestimations due to high formaldehyde solubility
• pure water as absorbing solution is uneffective, and is necessary to use 0,01n H2SO4 solution
• is not necessary to use DNPH to stabilise sampled solution in field, but is possible to do it within 48 hours from sampling, in laboratory
• after stabilisation with DNPH, is necessary to let samples rest for at least 24 hours, in order to let full development of stabilisation reactions
• after stabilisation, samples are stable for at least 15 days
• HPLC and spectrophotometry give similar results.

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