Energy loss during air flow through biofilter media: - Impact of entrance region minor loss, biomass accumulation and media

Høimark, Røskva Lill Lindgård

10. term

Master of Science in Environmental Engineering

2012

2012-06-14

51 pages

Fokusset i dette projekt er, at identificere og kvantificere enkelttabene og energitabene hen over ind-og udløbet af forskellige biofilter med forskellige luft flow. Undersøgelsen af enkelt-tab afhængighed af biofiltre medies karakteregenskaber og flow betingelser, hvilke blev udført ved brug af fem forskellige laboratorieskala biofilterenheder. Til dette formål var trykvariationen hen over de forskellige filterenheder målt før indløbet, indeni filteret og efter udløbet, under en række forskellige strømningshastigheder. Målingerne viste, at filtermaterialets egenskaber, såsom porestørrelse og pore retning har en signifikant indflydelse på trykvariation hen over filterenheden. Endvidere blev variationer i gas-energi niveau hen over filterenhederne målt og blev med succes modelleret. Modelleringen bekræftede, at både porestørrelsen og pore retningen har en signifikant indflydelse på enkelt-energitabene hen over indgangen til filterene. Yderligere blev tryktabets målinger udført på en fuldskala biofilterenhed placeret ved et svineproduktionsanlæg. Resultaterne viste, at tilstedeværelsen af biofilm indeni biofilter materialet kan have en signifikant indvirkning på tryktabet, som generelt set falder hurtig med stigende biofilm tykkelse. Resultaterne viste også, at biofilm densiteten indeni biofilteret varierer efter placering, men er generelt højere nær indløbet. Der konkluderes, at der findes enkelt-tryktab og energitab hen over ind- og udløbet af biofilter medier (noget, der ikke tidligere er blevet dokumenteret), og at det er muligt at modellere disse tab.

The focus of the project is to identify and quantify the minor energy losses over the entry and exit during gas flow through biofilter materials. The investigation, of minor loss dependency on biofilter medium characteristics and flow conditions, was carried out using five different laboratory scale biofilter units. For this purpose the gas pressure variation across the different filter units were measured for a range of different gas flow velocities, before the inlet, inside and after the outlet of the filter units. The measurements showed that filter material characteristics such as pore size and pore orientation have a significant impact on the pressure variation across the filter units. In addition the variations in gas energy level across the filter units was measured and successfully modelled. The modelling confirmed that both pore size and pore orientation have a significant influence on the minor energy losses over the inlet of the filter. Additional measurements of pressure loss were carried out on a full scale biofilter unit located at a pig production facility. The result showed that the presence of a biofilm inside the biofilter material can have a very significant impact on the pressure loss. In general pressure loss increase rapidly with increasing biofilm thickness. The results also showed that biofilm density within the biofilter material varies with location, but is generally higher near the inlet. In conclusion this project shows that there exist minor pressure and energy losses over the inlet and outlet of biofilter media (something that has not previously been documented) and that it is possible to model these losses.

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