Use Of Gas Recirculation Research Articles

Towards more eco-friendly gaseous detectors

In the last years, the particle detector community faced a new challenge: how to convert existing and future gaseous detectors in more eco-friendly ones. Indeed, several detectors make use of greenhouse gases (GHGs) since they allow achieving excellent performance and long-term stability. With a growing concern on climate change and future restrictions, it is fundamental to look for solutions that can balance detector performance with an eco-friendly approach. CERN was a pioneer in developing strategies to reduce the use of GHGs in particle detection. Three different strategies have been implemented: the use of gas recirculation and recuperation systems for existing and future detector systems and the search of alternative eco-friendly gas mixtures. Thanks to the first two approaches, it is possible to recycle the gas mixture supplied to the detectors and to retrieve GHGs from the used gas mixtures, allowing a reduction of GHG emissions up to 95%–100% at the LHC experiments. By looking at the long-term operation and future particle detector applications, the search of alternative eco-friendly gas mixtures must be envisaged. A big effort is on-going for the C2H2F4 replacement for the Resistive Plate Chamber (RPC) detectors, which nowadays account for most of CERN particle detector emissions. Several eco-friendly gas mixtures have been identified and tested but finding a suitable replacement for the LHC experiments is particularly challenging. Alternatives to SF6, which is the most powerful GHG, are under studies for RPCs in term of detector performance and chemical characterisation. Last point is increasingly crucial since most of the so-called eco-friendly gases belong to the PFAS family which is very likely to be subject to new regulations soon.

Ensuring the Environmental Friendliness of Drillships during Their Operation in Special Ecological Regions of Northern Europe

The features of the operation of the drillship-type vessels in special ecological regions of Northern Europe are considered. The main gap in the study of these systems is to determine the optimal degree of recirculation. The requirements of the International Maritime Organization for the emission of nitrogen oxides from the exhaust gases of marine diesel engines are given. The aim of the study is to determine the optimal degree of recirculation of exhaust gases of a 16V32 STX-MAN marine diesel. During the research, the optimal degree of exhaust gas recirculation varied in the range of 0–21%, the load on the diesel—in the range of 35–95% of the rated power. It was established that in this case, the emission of nitrogen oxides decreases up to 7.7–33.6%, the specific fuel consumption increases up to 0.2–3.5%. It was also found that the use of gas recirculation in the range of 18–21% at loads of 35–55% leads to a critical increase in exhaust gas temperature. It is advisable to use exhaust gas recirculation in the range of 6–15% to ensure the environmental friendliness of the operation of the drillships. In these modes, the maximum reduction in nitrogen oxide emissions is ensured with a minimum increase in specific fuel consumption. Future studies should be directed at the development of the criteria for the environmental stability of sea vessels.

CARBON NANOMATERIAL PRODUCTION FROM PRODUCTS OF METHANE-AIR CONVERSION WITH SPENT GASES RECIRCULATION

The possibility of increasing of a specific yield of carbon nanomaterial from the products of methane-air conversion through the use of spent gases recirculation is considered. The analysis of the influence of water vapor and carbon dioxide contained in the recirculated gases on the methane conversion has been performed. According to the developed calculation method, the assessment of changes in the main parameters of carbon material synthesis was done. Evaluation was performed depending on the degree of recirculation of spent gases in the transition and steady-state periods of the process. It is shown that the use of gas recirculation increases the specific yield of the carbon material, but in this case, due to the accumulation of nitrogen in the gas phase, there is a decrease in the productivity of the process for the resulting product. The evaluation of the productivity enhancing by rising of the gases pressure in the system was made. It has been established that in order to increase the specific yield of carbon material, the obtained converted gas and reusable recirculated gas should be subjected to deep purification from water vapor. Bibl. 16, Fig. 6, Tab. 2.