NUCLEAR TECHNOLOGIES AND METHODS 133 SAMPLE COLLECTION AND PREPARATION FOR CO2 ISOTOPIC ANALYSIS IN INDUSTRIAL OFF-GASES Krzysztof Plewka, Ryszard Wierzchnicki The analysis of isotope ratios is a new method to sample from a vessel connected to a glass vacuum study of greenhouse gases origin and to investi- line and it is purified by standard cryogenic tech- gate their chemical reaction pathways [1-2]. The niques. The purification system consists of two cold main aim of the work was to elaborate a method traps. The first trap is designed for H2O condensa- for measuring isotopic composition of greenhouse tion; it is dipped in acetone chilled by liquid N2 to o gases (CO2, CH4 and N2O) emitted from chosen -73±3 C. The second trap serves to freezing CO2 o industrial processes. The first stage of realization and is dipped in LN2 at -196 C. Initially, the vessel of the project is the collection of gas samples and with the sample is connected to the vacuum line –4 extraction of CO2 for isotopic measurements [3-5]. via an o-ring joint and the line is evacuated to 10 A portable gas sampler was constructed for col- mbar. The gas accumulated in the vessel is trans- lection of gas samples at fieldwork (Fig.1). From ferred to the vacuum line and condensable com- each of the gas sampling ports, which are situated pounds are caught in cold traps. Non-condensable at the electrofilter exit, the gases are collected to gases are pumped away. The second cold trap is o three types of glass vessels. The first glass vessel is warmed to approximately 30 C to release CO2, for a vacuum purification system, the second for a while H2O remains frozen in the first trap. Liberated continuous flow purification system and the third CO2 is transferred to another glass sample vessel, one is for gas chromatography analysis. Before which is subsequently connected to the dual inlet sampling, the vessels are filled with pure helium system of the isotope ratio mass spectrometer DELTAplus (Thermo Finningan Bremen, Germany). The measurement is performed in relation to the working standard of CO2. Continuous purification system (Fig.3) has been constructed as an alternative for the vacuum puri- Fig.1. Portable gas sampler: 1 – warmed probe with two fication system for the separation of CO2 originat- ceramic filters situated coaxially, 2 – U-shape dryer filled ing from industrial processes. Carbon dioxide ex- with magnesium perchlorate anhydrous 6÷18 mesh and traction process, similarly as in the vacuum line, indicated silica gel, 3 – diaphragm pump, 4 – flow meter consists in the cryogenic separation of CO from a with maximum flow 5.0 LPM, 5 – gas vessels. 2 gas sample. The main part of the line are two heli- in the laboratory to prevent contamination from earlier samples or ambient air. The sampling set is equipped with a small diaphragm pump (12 V) (N 86 KTDCB: KNF Neuberger GmbH) with an efficiency of 360 LPH supplied with a battery (DC12V/7Ah). Combustion gases enter the sam- pler at a rate of 5 LPM by a warmed probe with ceramic filters situated coaxially. Since the tem- perature of gases is about 150oC, it is necessary to use the warmed probe to prevent condensation of water on the ceramic filters. Then, the warmed gas enters U-shape dryers filled with magnesium per- chlorate anhydrous and indicated silica gel. Col- lection of one sample takes about 3 min, which is Fig.3. Continuous flow purification system: 1 – gas cylinder the time needed to flush ten times each of glass with pure helium (99.9995%), 2 – pressure controller, 3 – vessels. glass vessel with 3-way PTFE key, 4 – helicoidal cold trap For CO separation from industrial off-gas 2 for water, 5 – helicoidal cold trap for CO2 with vacuum-valves samples, a special vacuum purification system was and o-ring joint, 6 – flow meter. elaborated (Fig.2). In this method CO2 is sepa- rated from other gasses by expansion of the gas coidal glass traps which act in the same way like in previous line. The second cold trap for CO2 is equipped with vacuum-valves and an o-ring joint used for connection to spectrometer. Glass ele- ments of the line are jointed by silicone tubes. After connection the glass vessel in the line, it is flushed ten times with pure helium at a rate of 1 LPM trough a bypass installed on the vessel. This is necessary to prevent contamination from earlier Fig.2. Vacuum purification system: 1 – glass vessel with samples or ambient air. In the second step, the · –2 vacuum-valves, 2 – cold trap for water, 3 – helicoidal cold flow rate is reduced to 8 10 LPM. Helium is used trap for CO2, 4 – pressure gauge, 5 – glass vessel cold trap as a carrier gas which flows trough the vessel filled for CO2, 6 – cold trap. with the sample and then enters the cold traps. 134 PROCESS ENGINEERING The whole line is flushed ten times. Condensable References compounds are caught in the cold traps. Non-con- densable gases are flushed away. In the sec- [1]. Stabe isotope measurement techniques for atmospheric greenhouse gases. IAEA, Vienna 2002. IAEA-TEC- ond helix frized CO2 and helium gas are trapped. Taking into account that working standard is pure DOC-1268. [2]. Isotope aided studies of atmospheric carbon dioxide CO2, it is necessary to pump away helium from the second trap, while CO remains frozen. After that and other greenhouse gases, Phase II. IAEA, Vienna 2 2002. IAEA-TECDOC-1269. procedure, the sample is ready for measurement [3]. Bertolini T., Rubino M., Lubritto C.: J. Mass Spectrom., in IRMS (isotope ratio mass spectrometer). 40, 1104-1108 (2005). The work was performed in the framework of [4]. Werner R., Rothe M., Brand W.: Rapid Commun. the project No. PBZ-MEiN-3/2/2006 ”Process en- Mass Spectrom., 15, 2152-2167 (2001). gineering for hazardous and greenhouse gases [5]. Iwata R., Ido T., Kovacs Z., Mahunka I.: Appl. Radiat. emission control and utilization” („InŜynieria pro- Isot., 48, 4, 483-485 (1997). cesów ograniczania emisji oraz utylizacji gazów szkodliwych i cieplarnianych”). PREPARATION AND CHRACTERIZATION OF PVDF MEMBRANES FOR ENVIRONMENTAL APPLICATIONS Marian Harasimowicz, Mohamed Khayet1/, GraŜyna Zakrzewska-Trznadel 1/ Faculty of Physics, Complutense University of Madrid, Spain Polyvinylidene fluoride (PVDF) is an excellent membranes for membrane distillation (MD) were polymer material with high chemical resistance for prepared by the method elaborated by Khayet and acid, alkali and organic solvents. Flat-sheet porous Matsuura [1]. The concentration of PVDF in the A B Fig.1. Membranes prepared with 12 wt% PVDF (Mw=275 000, Aldrich), 3 wt% LiCl (99%, ACS Reagent, Aldrich), N,N-dimethyl acetamide (DMAC, anhydrous 99.8%, Sigma-Aldrich): A – without silica, B – with 1 g/100 g silica (SiO2) fumed (particle size – 0.014 Pm, surface area – 200±25 m2/g (Sigma-Aldrich))..