Assessment of NH3 Reduction and N2O Production during Treatment of Exhausted Air from Fattening Pigs Building by a Commercial Scrubber

The use of air scrubbers to reduce ammonia (NH3) emissions from buildings on pig farms is one of the most promising techniques in the GÖteborg protocol and other European regulations including the Industrial Emission Directive. In France, some air scrubbers are currently used on pig farms, mainly to reduce odours from livestock buildings. However, recent research revealed the production of N2O resulting from the treatment of air from pig buildings. In this context, a two-month study was conducted on a pig farm with 750 places for fattening pigs to check the abatement of NH3 emissions and to assess the possible production of N2O during treatment of exhausted air from buildings housing fattening pigs by a air scrubber. Concentrations of NH3 and N2O in the inlet and outlet air of the scrubber were continuously monitored using an Innova 1412 infrared analyzer. With the scrubber operating parameters (airflow, design, size), our results confirmed the production of N2O in the order of 5% of NH3-N reduced. N2O was produced by biological nitrification and/or denitrification inside the air scrubber. Statistical analysis (Pearson’s test) showed that the production of N2O was strongly influenced by the rate of airflow and the outside temperature. The abatement of NH3 emissions from the building was only 33%, i.e. much lower than the 70% - 90% usually cited in the literature.

Catalytic decomposition performance for O_3 and NO_2 in humid indoor air on a MnO_x/Al_2O_3 catalyst modified by a cost-effective chemical grafting method

Processes based on non-thermal plasma（NTP） for indoor air treatment inevitably lead to the formation of toxic by-products such as ozone（O3） and nitrogen oxides（NOx）. Adding a step of heterogeneous catalysis in series with NTP could allow for the decomposition of the by-products. Therefore, different catalysts were developed based on transition metal oxides, such as NiOx, CoOxand MnOxwith different weight percentage 1, 5 and 10 wt.%,deposited on a γ-Al2O3 support. The O3 removal efficiency（ORE） and the NOxremoval efficiency（NRE） were very encouraging in dry air： about 65% and 80%, respectively, by using2 g 5 wt.% MnOx/Al2O3 catalyst under the experimental conditions. However, strongly negative effects of relative humidity（RH） on the catalytic decomposition performance were observed. To overcome this limitation, the catalyst surface was modified to make it hydrophobic using a cost-effective chemical grafting method. This treatment consisted in impregnating the 5 wt.% MnOx/Al2O3 catalyst with different trichloro（alkyl）silanes（TCAS）.The effects of different linker lengths and amounts of TCAS for the hydrophobicity and the decomposition performance of surface-modified catalysts under humid conditions were investigated. Our results show that the surface-modified catalyst with the shortest linker and 0.25 mmol/gcatof modifying agent represents the best catalytic decomposition performance for O3. Its ORE is 41% at 60% RH, which is twice that of the non-modified catalyst.

Experimental investigation on SPS casing treatment with bias flow

Generally, casing treatment（CT） is a passivity method to enhance the stall margin of fan/compressor. A novel casing treatment based on the small disturbance theory and vortex and wave interaction suggestion is a method combining passive control and active control, which has been proved effective at enhancing the stall margin of fan/compressor in experiment. In order to investigate the mechanism of this kind of casing treatment, an experimental investigation of a stall precursor-suppressed（SPS） casing treatment with air suction or blowing air is conducted in the present paper. The SPS casing treatment is designed to suppressing stall precursors to realize stall margin enhancement in turbomachinery. The experimental results show that the casing treatment with blowing air of small quantity can improve the stall margin by about 8% with about 1% efficiency loss. By contrast, the SPS casing treatment with micro-bias flow does not improve the stall margin much more than that without bias flow, even worse. Meanwhile, the present investigation has also attempted to reveal the mechanism of stall margin improvement with the casing treatment.It is found that the stall margin improvements vary with the modification of the unsteady shedding flow and the unsteady wall boundary impedance. The experimental results agree fairly well with the theoretical prediction using a flow stability model of rotating stall.