Spectroscopic Identification on CO2 Separation from CH4 + CO2 Gas Mixtures Using Hydroquinone Clathrate Formation

The formation of hydroquinone (HQ) clathrate and the guest behaviors of binary (CH4 + CO2) gas mixtures were investigated by focusing on an application to separate CO2 from landfill gases. Spectroscopic measurements show that at two experimental pressures of 20 and 40 bar, CO2 molecules are preferentially captured in HQ clathrates regardless of the gas composition. In addition, preferential occupation by CO2 is observed more significantly when the formation pressure and the CH4 concentration are lower. Because the preferential occupation of CO2 is found with binary (CH4 + CO2) gas mixtures regardless of the composition of the feed gas, a clathrate-based process can be applied to CO2 separation or concentration from landfill gases or (CH4 + CO2) mixed gases.

PILOT-SCALE METHANE DEGRADATION BIOCOVER AT OPERATING LANDFILL

A landfill is a large bioreactor, in the body of which landfill gases are generated due to anaerobic degradation of organic material. According to European legislation, the emission of methane, one of the landfill gases, should be kept to a minimum as methane is a greenhouse gas and has a significant impact on our climate. With large volumes, methane can be used for energy production, but if the collection is uneconomic, an attractive option would be to cover the landfill with a bioactive layer to degrade methane in-situ. In operational Uikala sanitary landfill, Estonia, where active gas collection system exists, it was found that uncaptured gas could be degraded in bioactive cover layer. To check whether such cover layer could be built from fine fraction after mechanical biological treatment (MBT), two experimental cells were constructed (0-20 mm and 0-40 mm fractions). The paper presents the design of experimental cells, a description of materials for construction and construction process, and preliminary results. Measurement system was installed in both cells: gas wells at eight depths and on three locations on surface. Three-level lysimeters were installed to determine water balance. Research is planned for two years with monthly gas sampling. The objective of the work is proving which of the MBT fractions, 0-20 or 0-40 mm, function better for methane degradation. Confirmation of the methane degradation efficiency in fine MBT fraction is important not only from the ecological point of view. The use of a fine fraction as a material for methane degradation layer would reduce the cost of processing this fraction and become a good example to a circular economy since the landfill would be recultivated using its own resources.

Investigations on disposal of low-calorific landfill gases by a small scale fluidised bubbling bed combustion plant

Poor landfill gases cannot be used to drive gas engines or be burnt in gas flares. This follows why the combustion flame front velocity for poor gases becomes very low. From this moment the non-flammable poor landfill gases are polluting the environment. An energetical utilisation of very poor landfill gases is of ecological interest and is also an important contribution for climate protection. A feasible solution must be found. In our University lab we are using a Fluidised Bubbling Bed Combustion (SFBC) plant with 200 kW completed by heat exchangers for pre-heating the combustion air as well the combustion gas. In the past this SFBC-principle had successfully been applied to a thermal utilization of very different wastes. Using this principle we are able to recover the energy content of very poor landfill gases down to a concentration below the lower explosion limit. The fluidised red hot inertia bed material at a temperature of 850°C is an excellent ignition source to run the process at constant parameters within legal limits. Therefore we have very low pollutant emission levels. Using a developed mathematical SFBC-model we theoretically investigated the lowest possibly methane concentration limits under given pre-conditions as well as fluidised bed temperature level, fluidisation air and fuel gas temperatures, necessary oxygen concentration level. Following to these model investigations we realized their experi-mental verification in our 200 kW lab SFBC testing plant in a wide-spread plant load range. These lab tests had very successful results. The possible SFBC operation conditions have been estimated. Based on these results we engineered by the help of industrial partners a real SFBC plant installed on a closed landfill in Mecklenburg – Western Pomerania, 65 km far from our University lab. Using these plant we dispose there real very poor landfill gas. The landfill gas is poor enough to avoid a further operation of a common gas flare. The automatically operated SFBC process is running at 850 °C without any technical interruptions since one year. At the moment the maintenance rate is 3 weeks. The plant is supervised by data remote control. The contribution will compare the lab test results with the results of the real existing plant. If the poor landfill gas flow is strong enough the SFBC produces enough energy e.g. to drive a steam cycle or a gas turbine externally fired by the SFBC that generates electrical power. In this case the necessary power equipment has to be added to the SFBC plant.

Control of Landfill Gases Emission with Particular Emphasis on Btex

Control of Landfill Gases Emission with Particular Emphasis on BtexLandfilling is the most popular way for waste disposal and has been widely applied globally. A large quantity of volatile organic compounds (VOCs) is released from landfills. Among them, BTEX (benzene, toluene ethylbenzene and xylene) is a major group of pollutants, which have now become a cause for concern worldwide because of their toxic properties. For this reason, strict regulations have come into force which induce researchers to find methods to reduce their emissions. This article contains descriptions of several aerobic metabolic pathways for the degradation of BTEX, which are provided by two enzymatic systems (dioxygenases and monooxygenases). Special attention was paid to biofiltration - a method for improving the efficiency of treatment of BTEX released from landfills.