Impurities In Biogas Research Articles

Applicability of selected methods and sorbents to simultaneous removal of siloxanes and other impurities from biogas

This paper critically reviews and discusses the state-of-the-art technologies for the removal of siloxanes from biogas, which could be used to simultaneously remove other contaminants. The reasons for purifying biogas, the scope of this purification and the recommended (depending on the biogas utilization equipment) concentrations of volatile silicon-organic compounds are presented. Established and new promising methods of removing typical methylsiloxanes from biogases from municipal landfills and sewage sludge are characterized and analyzed. Their suitability for the simultaneous removal of other trace biogas impurities and possibilities of regenerating the spent sorbent are assessed. It is shown that the commonly used activated carbon is not suitable for comprehensive biogas treatment. On the basis of the analysis, an adsorption method using halloysite (a natural zeolite mineral) as an inexpensive, universal and regenerable adsorbent is proposed. The method can be used after physicochemical treatment to comprehensively purify biogas from methylsiloxanes, hydrogen sulfide, ammonia, halides and other technically and environmentally burdensome impurities. Some directions for further research in this regard and possible environmentally safe ways of utilizing the spent sorbent are indicated.

Continuous absorption of CO2 in packed column using MDEA solution for biomethane preparation

Nowadays, the energy consumption in Indonesia is increasing. Raising of energy consumption force Indonesia to find other energy resources. Biogas is one of the renewable energy, which was developed in anticipation to the fossil energy reduction. Reducing the content of impurities in biogas may reduce the corrosion impact and increase the combustion efficiency. The biomethane can be utilised as fuel for generator in small and medium scale industries (IKM). Continuous CO2 absorption in packed column using MDEA solution as absorbent is studied for biomethane preparation. CO2 absorption experiments was performed continuously in the packed absorption column with a diameter of 6 cm and 75 cm length. Gas is sparged from the bottom of the column while the liquid is pumped through the top of the column. The concentration of CO2 at exit gas is analysed by GC and recorded as a function of time. The flowrate of the inlet gas was varied at 1 LPM; 1.5 LPM; and 1.8 LPM. Variation of MDEA solution concentration used was 20% and 35.31%. Mathematical model for unsteady state CO2 absorption in packed column was developed. The reaction rate constant (k) and mass transfer coefficient KGa were determined by fitting the outlet CO2 concentration data as a function of time to the model solution with smallest Sum of Square of Errors (SSE). The experimental data shows that absorption of 1 LPM gas flow rate with 0,15 LPM MDEA solution flow rate may reduce 40 % CO2 to be 17 % CO2 in outlet gas. The steady state process reaches at 10 minutes. Increasing gas flow rates shows the higher overall mass transfer coefficient. The reaction rate constant is not affected by gas flow rate variation.

Biogas cleaning and upgrading with natural zeolites from tuffs

ABSTRACTCO2 adsorption on synthetic zeolites has become a consolidated approach for biogas upgrading to biomethane. As an alternative to synthetic zeolites, tuff waste from building industry was investigated in this study: indeed, this material is available at a low price and contains a high fraction of natural zeolites. A selective adsorption of CO2 and H2S towards CH4 was confirmed, allowing to obtain a high-purity biomethane (CO2 <2 g m−3, i.e. 0.1%; H2S <1.5 mg m−3), suitable for injection in national grids or as vehicle fuel. The loading capacity was found to be 45 g kg−1 and 40 mg kg−1, for CO2 and H2S, respectively. Synthetic gas mixtures and real biogas samples were used, and no significant effects due to biogas impurities (e.g. humidity, dust, moisture, etc.) were observed. Thermal and vacuum regenerations were also optimized and confirmed to be possible, without significant variations in efficiency. Hence, natural zeolites from tuffs may successfully be used in a pressure/vacuum swing adsorption process.

Hydrotalcite-dispersed paper-structured catalyst for the dry reforming of methane

A paper-structured catalyst (PSC) is a flexible planar catalyst that can be stacked on the anode of SOFCs and exhibits excellent catalytic activity for the reforming of hydrocarbon fuels at the operating temperature of the SOFC. Although our final goal is the realization of direct internal reforming (DIR) SOFCs fueled by biogas by applying a PSC, the tolerance of PSCs to sulfur impurities in biogas (H2S) must be improved for the practical application of PSCs to DIR-SOFCs operated by biogas. In this study, an inorganic fiber network in which a layered double hydroxide (Mg/Al-hydrotalcite denoted as HT) is dispersed was prepared by a paper-making process, and Ni was then loaded in this paper matrix via an impregnation process. This Ni-loaded HT-dispersed PSC exhibited considerably higher tolerance to H2S than that of HT-free PSC.

Feasibility Study of Pulse Detonation Engine Fueled by Biogas

The hottest issue toward the environment today is the Clean Development Mechanism (CDM) and Green House Gases (GHG) which influenced climate change. At the same time, the world is facing the crisis of limited reserves of petroleum-based fuel resource which is being continuously depleted. Therefore, these three issues can possibly be overcome by using alternative fuels such as biogas, biodiesel, biomass, biofuel, alcohol, vegetable oils etc. The use of biogas as fuel for Pulse Detonation Engine (PDE) possibly promise great advantages on power production with less emission. This is because PDE operates with higher thermodynamic efficiency by operating on constant volume pressure. Biogas usage will somewhat contributed to the CDM and and lessen the GHG issues. Here through detailed literature review, the challenges such as lower flame speed (compared to hydrocarbon fuel) and biogas impurities are discussed. Combustion characteristics of biogas in detonation mode are also investigated. Strategy is presented here for looking at the possibility of PDE operation using biogas.

Multiple regression analysis of hydrogen sulphide poisoning in molten carbonate fuel cells used for waste-to-energy conversions

Bioenergy addresses three important social concerns: security of energy supply, mitigation of greenhouse gas emissions and development of agriculture. Bioenergy is the energy generated by either direct or indirect combustion of biomass, which is non-fossil organic material of both vegetable and animal origins. Different technologies are currently available for bioenergy production, but fuel cells are one of the most interesting devices because of their environmental benefits and their high efficiency. In particular, molten carbonate fuel cells are suitable devices for waste-to-energy conversion because of their ability to be fed with biogas, which is biomass-derived gas rich in methane and carbon dioxide. Indeed, methane can be internally reformed to hydrogen, carbon dioxide is a safe diluent preventing electrolyte loss, and carbon monoxide acts both as a hydrogen supplier and as an actual fuel. Unfortunately, biogas impurities, such as sulfur, halogen and nitrogen compounds, cause adverse effects on cell performances. The most dangerous impurities are sulfur compounds, among whom hydrogen sulphide is the predominant and the most harmful chemicals. It reacts with nickel-based anode to form nickel sulphides, that block catalytic sites, slowing hydrogen oxidation down, and change the anode wettability in molten carbonates, compromising the optimal electrolyte distribution within cell components. Poisoning mechanism of hydrogen sulphide depends on operating conditions such as current density, anodic gas composition, temperature and pressure. The aim of this work is to study hydrogen sulphide effects on MCFCs by means of multiple regression analysis. The mathematical approach gives us tools to define the main sulfur poisoning mechanism under MCFC operating conditions, quantify the effects of the main parameters affecting poison actions, such as current density, hydrogen and hydrogen sulphide, and identify their mutual interactions. Also it is possible to formulate a multivariate model to predict sulfur poisoning.