A gas chromatography-quartz crystal microbalance for speciation of sulfur compounds in landfill gas.
A new method, based on separation with gas chromatography and detection with a quartz crystal microbalance, was used for the quantification of ethane-1-thiol, propane-1-thiol, ethyl methyl sulfide, propane-2-thiol, butane-2-thiol and butane-1-thiol. The analytical error, the analysis time and the general analytical performance are identical for gas chromatography-mass spectrometry (GC-MS) and gas chromatography-quartz crystal microbalance (GC-QCM). However, the GC-QCM method constitutes a low cost alternative to GC-MS for monitoring individual sulfur compounds in landfill gas. It is an easily assembled apparatus made with an injection device, a furnace, a column, a crystal cell and a quartz crystal.
Kaatopaikkakaasun puhdistaminen ja analysointimenetelmät
Organic matter deposited in landfills decomposes due to microbial action, forming landfill gas, which consists mainly of methane and carbon dioxide. Methane is a powerful greenhouse gas, which is burned in flares on landfills to prevent it from entering the atmosphere. It is also and excellent fuel; natural gas consists primaly of methane. Landfill gas collected from landfills can usually be used in power plants to produce heat and electricity without any refining. Landfill gas, however, also contains minor amounts of impurities, like sulphur compounds or siloxanes and halogen compounds. Upon burning, these compounds may cause corrosion and wear on boiler and engine parts, or pollute the environment by spreading from exhaust gases. Carbon dioxide and sulphur compounds as well as other impurities can be removed from landfill gas by various methods. Through purification the methane content is increased, after which the more energy efficient gas can be used as a vehicle fuel. In this thesis literature results on landfill gas composition were researched. Methane content in different places in the world was 40–60 %. Landfill gas composition varies, because different kinds of waste are deposited on all landfills, depending on local recycling conventions and waste treatment legislature. The composition varies even inside specific landfills due to inhomogeneous spread of waste. The gas formed in waste water treatment plants, on the other hand, is very homogeneous and usually has a methane content of over 60 %. In the experimental part of this thesis, enrichment of landfill gas from Mustankorkea landfill in Jyvaskyla was studied. The enrichment system was based on counter current water wash, where pressurised water (20−−23 bar) flowed towards a jet of gas, absorbing impurities in the gas. The raw gas contained on average 55 % of methane while the enriched product gas had a methane content of about 88 %. Siloxanes were not removed by the water wash, but they were removed by the dryer unit. The concentration of siloxane compounds D3, D4 and D5 were lowered to below 7 μg and other siloxanes dropped below the limits of detection. The most dominant VOC was toluene and its concentration in raw landfill gas was 4, 3 mg/m3, but it was also removed totally in the enrichment process. The amount of hydrogen sulphide dropped from 150 ppm to about 5 ppm in the purification process. The enriched landfill gas satisfies the requirements of the Swedish biogas standard on all other parts except on methane content (requirement is over 95 %). The extra carbon dioxide doesn’t cause other harm than lowering the range of the vehicle fueled by the gas. The enriched gas can be used as a fuel in powerplants and practically in cars as well.
The Application of Cryptand 22 as a Bifunctional Stationary Phase for Ion Chromatography
Poly (styrene/divinyl benzene) with cryptand 22 as an anchoring group was synthesized and applied as a bifunctional packing material for the separation of both cations and anions. At pH 10, the resin became a cation exchanger and successfully separated alkali metal ions such as Li+, K+ and Cs+ with methanol as eluent. The effects of solvents, flow rate and temperature on the separation of various ions were also investigated.